Marijuana & Driving Mega Thread

[Uzi578]

Part 4 of 4

DISCUSSION

Four studies preceded the present one in this series (Robbe & O'Hanlon, 1993). The first and third are relevant to this discussion. The former involved 23 experienced THC users who were allowed to continuously smoke marijuana cigarettes (THC, 2.57%) in a clinical environment until arriving at their desired "high." The preferred mean dose was close to 300 ~g/kg. A different group of 15 similarly experienced users completed the third study. On separate occasions, they smoked marijuana.placebo and marijuana delivering THC 100, 200 and 300 ~g/kg. The drug's effects on driving were assessed 55.170 min. post.dosing in essentially the same manner as during the present study. No dose significantly affected this group's car following performance but all elevated SDLP in the Road Tracking Test. Relative to the placebo level, mean SDLP rose by 1.1, 1.8 and 2.9 cm in rough proportion to the THC dose. Though all significant, these changes were very modest in comparison to those produced by alcohol and a number of medicinal drugs in previous investigations. Alcohol was used as the agent for calibrating the standard test (Louwerens et al, 1987). Social drinkers performed it on five separate occasions while their BACs were controlled in equal steps between 0.00 and 0.15 g/dl. The drinkers' mean SDLP rose exponentially with BAC (R=0.99) and an empirical equation was derived for describing the relationship. The equation has been subsequently used for describing drugs' effects on SDLP in terms of respective BAC equivalencies. When we applied it for describing THC's effects in the earlier study, the maximum mean change after 300 ~g/kg was found to be the equivalent of BAC=0.08 g/dl. THC's effects were also far less than those of some commonly used medicinal drugs. For example, after a week of receiving diazepam 5 me (Valium.), thrice daily, and lorazepam 2 me (Ativan.), twice daily, different groups of clinically anxious patients drove with mean SDLPs that were respectively 7 and 10 cm higher than baseline (Van Laar et al, 1992; O'Hanlon et al, 1995). Thus, we concluded that THC taken alone in doses preferred by its users does not seriously affect driving performance.

We originally intended to administer the same THC doses, alone and in combination with alcohol, in the present study. However, the results of a pilot study deterred us from using the 300 ~g/lcg dose. In combination with the specified alcohol dose, it rendered some subjects incapable of standing much less driving. We therefore proceeded to administer only the two lower doses, believing that these would be sufficient for determining the nature of THC's interaction with alcohol.

Subjects who participated in this study differed in several important respects from the predecessors. They were younger than the groups who defined the preferred dose and completed the earlier driving study (22.7 years in the present versus 25.7 and 26.8 in the previous studies); they had fewer years of driving experience (4.3 years versus 6.7 and 5.9 years); and, most importantly, their marijuana smoking frequency was less than half of either preceding group's (2.3 versus 5.8 and 5.4 times per month). These differences should be borne in mind while comparing the studies' results. One may reasonably assume that the older, more frequent THC users had driven more often under the drug's influence, and there is little doubt that the frequent use of any impairing drug fosters "behavioral tolerance" or state.related and task.specific learning to compensate for its influence on performance (review: Young and Goudie, 1994). Behavioral tolerance is unlike pharmacological tolerance that either lowers a drug's circulating concentration or diminishes its activity at receptor sites when taken continually in the same doses over days or weeks. Rather, behavioral tolerance develops as the user practices the task while intoxicated on occasions that can be widely separated in time. Given the present group's youth, limited driving experience and low rate of THC use, it seems unlikely that many could have developed the behavioral tolerance of the predecessors. Which group is more representative of THC users in general is an open question. Probably neither is truly representative, both were drawn from different bands in a very broad spectrum. If there is any distinction to be made, it is that the present group comprised a sample of relatively inexperienced THC users who might be especially vulnerable to the drug's impairing effects on driving.

These subjects' performance in the Road Tracking Test clearly showed the adverse effects of alcohol and THC. Alcohol alone caused mean SDLP to rise by 2.2 cm over the placebo level. That change was almost exactly as predicted from Louwerens et als equation for drivers operating with BAC=0.05 g/dl. Thus the present group demonstrated their normal sensitivity to this impairing effect of alcohol on driving. Separate doses of 100 and 200 ,ug/kg caused mean SDLP to rise by 2.7 and 3.5 cm, respectively. These changes were well above those shown after the same doses by the earlier group. Yet despite the absolute differences, the increments in both groups' mean SDLPs as their doses increased from 100 to 200 1lg/kg were practically the same; i.e., 0.8 and 0.7 cm, respectively. This suggests that while the minimum dose for affecting the present group's driving performance was lower, their dose.response was almost identical to the previous group's whose greater resistance to THC's effect on driving performance could be the consequence of behavioral or pharmacological tolerance, or both.

The effects of combined alcohol and THC on the present subjects' road tracking performance were severe. Alcohol plus THC 100 and 200 ~g/kg respectively elevated mean SDLP by 5.3 and 8.5 cm. The former change was comparable to that predicted from Louwerens et als equation for driving with BAC=0.09 g/dl. The latter change was equivalent to driving with BAC=0. 14 g/dl. It has only been exceeded in all studies employing the standard test by that occurring after lorazepam 2 mg (see above). Judging from SDLP, the subjects' performance deteriorated more after both combinations than it would have if they simply had driven after consuming enough alcohol to become legally intoxicated.

The subjects' progressive loss of control over the vehicle's lateral position as the drugs' effects went from bad to worse first led to rising SDLP, and later, TOL. The relationship between mean SDLP and TOL across both test repetitions in every condition is shown in Figure 4.1. The function describing that relationship was derived from least.squares regression analysis following an exponential model: TOL=0.00359e° ~849~tSD~P'. The model was selected on the basis of a mathematical argument by Allen and O~anlon (1979). Those authors showed that TOL must necessarily increase as an exponential function of SDLP so long as drivers generally operate with a Gaussian distribution of lateral position around a stable mean. In any case, the empirical equation adequately describes the data (R2=0.89). It implies that the subjects' SDLPs could not have risen much further without a totally unacceptable increase in TOL. As it was, while mean SDLP increased from the lowest to the highest values in this study by 43%, mean TOL rose by 474%.

Figure 4.1 Geometric mean TOL as a function of mean SDLP across conditions: OO ( ), OTT (O), OT2 (I), AO (I), ATE (I), AT2 (I). (For definition of treatment conditions, see Table 2.1.)

The exponential rise in TOL from conditions where alcohol and THC were separately administered to those where they were given in combination suggests a synergistic interaction. However, the statistical test failed to show a significant interaction between alcohol and THC effects on TOL. But TOL was little affected by any treatment other than the combinations. By taking the data from all conditions together into a single analysis, 2/3 of them mainly contributed error variance. Regardless of the additivity or multiplicity of the drugs' effects, there can be no doubt that their combination is potentially very dangerous for driving. Neither drug's doses in this study were particularly high and one may reasonably suppose that drivers in the real world occasionally operate after consuming more of one or both in combination. If they do, our results suggest that their increasingly large and frequent excursions from the relative safety of a traffic lane would occupy a considerably greater percentage of the distance traveled. This alone would increase the driver's risk of losing control as the vehicle leaves the paved surface of the road, of striking a fixed object at roadside or of swerving into the path of an approaching or overtaking vehicle. The risks of all types of collisions could rise in parallel if, as is thought, the loss of lateral position control is but one sign of general driving impairment.

An indication that the drugs' adverse influence on driving performance was pervasive came from the Car Following Test. Despite missing data which necessitated an unparsimonious and relatively weak analysis, its results supported those from the other driving test. Changes in mean RT and HSD roughly paralleled those in mean SDLP. Performance after placebo was always the best, and after the combination of alcohol and THC 200 ~g/kg, always the worst. THC dose effects, with and without alcohol were apparent for all performance measures. Mean RT did not differ significantly after drug and placebo treatments, except in the worst case. Yet those differences were large in practical terms. The difference due to the combined effect of alcohol and THC 200 ~g/kg was 1.6 sec. Since the average speed in that condition was about 97 km/in (59 mph), this delay meant that the vehicle traveled, on the average, an additional 42 m (139 fit) beyond the point where the subjects began to decelerate after placebo treatment. Even the lowest THC dose, by itself, retarded the subjects' mean RT by 0.9 sec. In that case, they "only" drove an additional 24 m (78 fit) before beginning to decelerate. It does not take much effort to imagine how response delays between 0.9 and 1.6 sec could affect safety in real car following.

The drugs' effect on mean HSD was clearer: that parameter was significantly affected by every drug treatment. The changes in mean HSD reveal another adverse drug effect on driving; i.e., diminished ability to perceive changes in the relative velocities of other vehicles and/or diminished ability to adjust one's own vehicle's speed accordingly. They also indicate a subtle hazard the.drug user might pose for other drivers operating in traffic platoons during high speed travel on highways. The changes from OO to AT2 in this study were about 2.m during both acceleration and deceleration maneuvers. Assuming a Gaussian distribution of headway variance, this means that the subjects' total range of to and fro oscillation increased by about 12 m (i.e., 6 x AHSD) or 39 fit under the combined influence of alcohol and THC 200 1lg/kg. In real life, that abnormal headway variability would be transmitted to and amplified by every driver/vehicle in retrograde succession (i.e., the "accordion effect"). Unless succeeding drivers compensated by opening the gaps between vehicles, one in the series would find it impossible to react quickly enough to avoid a collision.

Despite the observed impairments, the subjects seemed well aware of their impairment in both tests. Their self.ratings of driving quality varied over conditions in general agreement with the objective measurements. The instructors rated their driving quality as even lower but the differences in these assessments were not large. Some subjects, particularly after THC 200 ~g/kg alone or in combination with alcohol, indicated that they had failed the tests. Why they continued to drive in these conditions is a good question. They probably would not have proceeded, nor undertaken the tests in the first place, were it not for their reliance on the instructors to prevent untoward consequences. Though reliance on the instructor was definitely not encouraged, it may be an inevitable artifact of this experimental approach. A further indication that participation in an experiment encouraged the subjects to drive when they ordinarily would not may be taken from their previous histories. Whereas all subjects admitted previously driving under the influence of THC, only three men said they had done so after using alcohol and THC in combination.

Finally, something should be mentioned about the observers' comments. Though unsystematic and probably biased by general knowledge of the subjects' treatments, these supported the objective results and also revealed some idiosyncratic reactions that would have otherwise gone undetected. In general, the subjects remained responsive to the instructors' occasional corrections. Only one woman drove in a manner they considered "reckless", and even she followed their instructions, if only briefly. Poor attention to the driving task and deficient control over the vehicle's speed and lateral position were the most frequently observed signs of the subjects' impairment. Memory disturbances afflicting four subjects after combined drug treatments were the most dramatic. They suddenly failed to recall what should have been very familiar test procedures. Many drugs, such as alcohol and the benzodiazepines, interfere with the acquisition and/or later recall of information while the drug is active in the brain. None of them is known to consistently prevent the recall of well practiced procedures. That THC occasionally did so in this, our earlier studies, and one other study (Yesavage, 1985), suggests that the drug may possess unique amnestic properties. The phenomenon is worthy of further investigation.

CONCLUSIONS
5.1 General Conclusions

In a previous series of studies on the effects of THC alone we concluded that THC given in doses up to 300 1lg/kg has "slight" effects on driving performance (Robbe & O'Hanlon, 1993). The results of the present study now compel us to revise that conclusion. The present subjects' performance was more affected than their predecessors'. The present subjects showed impaired car following performance after THC 100 1lg/kg whereas the previous ones were not impaired by doses up to 300 1lg/kg. In the present study, road tracking performance after 200 ~g/kg was worse than the performance after 300 ~g/kg in the previous study. We believe that these differences are attributable to the groups' respective experience with THC smoking and to driving under the influence of THC. The present group was less experienced and probably had not developed the same degree of behavioral tolerance as their predecessors. Yet all of the individuals in both groups admitted to having occasionally driven under the influence of THC before entering the studies. Thus, the new data seem no less representative of how drivers normally operate under the influence of THC. The addition of these data to those previously collected merely broadens the range of reactions that might be expected to occur in real life. That range has not been shown to extend into the area that can rightfully be regarded as dangerous or an obviously unacceptable threat to public safety. Alcohol present in blood concentrations around the legal limit (0.10 g/dl) in most American States is more impairing than anything subjects have shown after THC alone in our studies. As mentioned, medicinal drugs have had worse effects on psychiatric patients' driving performance in other studies employing the same test procedures. If not blatantly dangerous, however, the effects of THC alone in this study were certainly more than slight. They were of sufficient magnitude to warrant concern. Drivers suffering the same degrees of impairment as the present subjects did after THC alone would be less than normally able to avoid collisions if confronted with the sudden need for evasive action. They would probably also be more likely to fall asleep during prolonged vehicle operation. In short, while the effects of THC alone in doses up to 200 1lg/kg might be categorized as "moderate" in the tests, they could easily become "severe" under exceptional circumstances.

The subjects' reactions to combined use of alcohol and THC are another matter. Drivers suffering the same degrees of impairment as the present subjects did after THC and alcohol, combined, would be exceedingly dangerous. Their impairment would be a serious threat to their own safety, and perhaps to the general driving public as well. The simultaneous consumption of low to moderate doses of alcohol and THC, rendered the present subjects incapable of safe driving for several hours thereafter. That they were able to safely demonstrate their impairment was, on occasion, only possible because of the instructor's intervention. Had these individuals attempted to drive alone in that condition, it is quite possible that one or more would have caused a collision.

5.2 Specific Conclusions

    * THC alone in 100.200 ug/kg doses impairs fundamental road tracking ability with the degree of impairment increasing as a function of the dose.

    * The impairment from THC alone does not diminish and may even increase for up to 21 hours after marijuana smoking, regardless of the THC dose.
    * THC in 100.200 ug/kg doses, in combination with alcohol sufficient for producing BAC=0.04 g/dl, severely impairs road tracking ability with the degree of impairment again increasing with the THC dose.
    * THC and alcohol effects on road tracking ability appear to be additive in a pharmacological sense, but the risk of driving off the road increases exponentially with the combined drug effect.
    * THC alone in 100- 200 ug/kg doses can impair the ability to maintain a constant headway while attempting to match velocity with a preceding vehicle.
    * THC 200 ug/kg in combination with alcohol seriously retards reaction time to the deceleration of a preceding vehicle.
    * The effects of THC and alcohol on headway maintenance and reaction time also appear to be additive but the sum in both cases can be large and potentially dangerous.

References

    * Allen RW, O'Hanlon JF (1979). Driver steering performance effects of roadway delineation and visibility conditions. Proceedings of Transportation Research Board Annual Meeting. (Washington DC) Paper No. 229.
    * Attwood DA, Williams RD, Bowser IS, McBurney LJ, Frecker RC (1981). The Effects of Moderate Levels of Alcohol and Marijuana, Alone and in Combination on Closed.Course Driving Performance. Tech Rep 81.RSU.17, Defense and Civil Institute of Environmental Medicine, Downsview, Ontario.
    * Brookhuis KA, Volkerts ER, O'Hanlon JF (1987). The Effects of some anxiolytics on car.following performance in real traffic. In: PC Noordzij, R Roszback (Eds.), Alcohol, Drugs and Traffic Safety . T86, Excerpta Medica, Amsterdam, 223.226.
    * Budd RD, Muto JJ, Wong JK (1989). Drugs of abuse found in fatally injured drivers in Los Angeles County. DrugandAlcoholDependence, 23, 153.158.
    * Casswell S (1979). Cannabis and Alcohol: Effects on closed.course driving behavior. In: I Johnson (Ed.) Seventh International Conference on Alcohol, Drugs and Traffic Safety. Australian Government Publishing Service, Canberra, 23.28.
    * Chesher GB (1986). The effects of alcohol and marijuana in combination: A review. Alcohol, Drugs and Driving, 2, 105.120.
    * Cimbura G. Warren RA, Bennett RC, Lucas DM, Simpson HM (1980). Drugs detected in fatally injured drivers and pedestrians in the Province of Ontario. Traffic Injury Research Foundation of Canada, Ottawa.
    * Cimbura G. Lucas DM, Bennett RC, Warren RA, Simpson HM (1982). Incidence and toxicological aspects of drugs detected in 484 fatally injured drivers and pedestrians in Ontario. Journal of Forensic Sciences, 27, 855.867.
    * Daldrup T. Reudenbach G. Kimm K (1987). Cannabis und Alkohol im Strassenverkehr. Blutalkohol, 24, 144.156.
    * Donelson AC, Cimbura G. Bennett RC, Lucas DM (1985). The Ontario monitoringproject: Cannabis and alcohol use among drivers and pedestrians fatally injured in motor vehicle accidents from March 1982 through July 1984. Traffic Injury Research foundation of Canada, Ottawa.
    * Garriott JC, Di Maio VIM, Rodriguez RG (1986). Detection of cannabinoids in homicide victims and motor vehicle fatalities. Journal of Forensic Sciences, 31, 1274.1282.
    * Louwerens JW, Gloerich ABM, De Vries G. Brookhuis KA, O'Hanlon JF (1987). The relationship between drivers, blood alcohol concentration (BAC) and actual driving performance during high speed travel. In: PC Noordzij, R Roszbach (Eds.) Alcohol, Drugs and Traffic Safety . T86, Excerpta Medica, Amsterdam, 183.192.
    * McLean S. Parsons RS, Chesterman RB, Dineen R. Johnson MG, Davies NW (1987). Drugs, alcohol and road accidents in Tasmania. The Medical Journal of Australia, 147, 6.11.
    * O'Hanlon JF (1984). Driving performance under the influence of drugs: Rationale for, and application of, a new test. British Journal of Clinical Pharmacology, 18, 121S.129S.
    * O'Hanlon JF, Ramaekers JG (1995). Antihistamines and actual driving performance in a standard test: A summary of Dutch experience, 1987.1994. Allergy, 50, 234.242.
    * O'Hanlon JF, Vermeeren A, Uiterwijk MMC, van Veggel LMA, Swijgman HF (1995). Amaolytics' effects on the actual driving performance of patients and healthy volunteers in a standardized test: An integration of three studies. Neuropsychobiology, 31, 81.88.
    * O'Hanlon JF, Brookhuis KA, Lonwerens JW, Volkerts ER (1986). Performance testing as part of drug registration. In: JF O'Hanlon, JJ de Gier (Eds.). Drugs and Driving, Taylor & Francis: London, 311.330.
    * Overall JE, Rhoades HM (1985). Adjusting p values for multiple tests of significance. In: HY Meltzer (Ed.) Psychopharmacology: The Third Generation of Progress, Raven Press, New York, 1013.1018.
    * Peck RC, Biasotti A, Borland PN, Mallory C, Reeve V (1989).The effects of marijuana and alcohol on actual driving performance. Alcohol, Drugs and Driving, 2, 135. 154.
    * Ramaekers JG, O'Hanlon JF (1994). Acrivastine, terfenadine and diphenhydramine effects on several aspects of driving performance as a function of dose and time after dosing. European Journal of Clinical Pharmacology, 47, 261.266.
    * Robbe HWJ (1994). Influence of Marijuana on Driving Institute for Human Psycho.pharmacology, University of Maastricht.
    * Robbe HWJ, O'Hanlon JF (1993). Marijuana and Actual Driving Performance, DOT HS 808 078, National Highway Traffic Safety Administration, US Department of Transportation, Washington D.C.
    * Smiley AM (1989). Marijuana: On.road and driving simulator studies. Alcohol, Drugs and Driving, 2, 121.134.
    * Smiley AM, Noy YI, Tostowary KW (1987). The effects of marijuana alone and in combination with alcohol on driving performance. In: PC Noordzij and R Roszbach (Eds.) Alcohol Drugs and Traffic Safety . T86. Excerpta Medica, Amsterdam, 203.206.
    * Soderstrom CA, Trifillis AL, Shankar BS, Clark WE, Cowley RA (1988). Marijuana and alcohol use among 1023 trauma patients. Archives of Surgery, 123, 733.737.
    * Stein AC, Allen RW, Cook ML, Karl RL (1983). A Simulator Study of the Combined E;ffects of Alcohol and Marijuana on Driving Behavior. DOT HS 806 405, National Highway Traffic Safety Administration. US Department of Transportation, Washington D.C.
    * Terhune KW (1982). The Role of Alcohol, Marijuana and Other Drugs in the Accidents of Injured Drivers. Calspan Field Services Inc., Buffalo, New York. Tech. Rep. under Contract No. DOT.HS.5.01179.
    * Terhune KW, Ippolito CA, Hendriks DL, Michalovic JG (1992). The Incidence and Role of Drugs in Fatally Injured Drivers. National Highway Traffic Safety Administration, US Department of Transportation, Washington D.C. Final Rep under Contract No. DTNH 22.88.C.07069
    * Van Laar MW, Volkerts ER, Willigenberg AAP (1992). Therapeutic effects and effects on actual driving performance of chronically administered buspirone and diazepam in anxious outpatients. Journal of Clinical Psychopharmacology, 12, 86.95.
    * Vuorman EFPM, Muntjewerff ND, Uiterwijk MMO, van Veggel LMA, Crevoisier C, Haglund L, Kinsig M, O~anlon JF (1996). Effects of mefloquine alone and with alcohol on psychomotor and driving performance. European Journal of Clinical Pharmacology, 50, 475.482.
    * Williams AF, Peat MA, Crouch DJ, Wells JK, Finkle BS (1985). Drugs in fatally injured young drivers. Public Health Reports, 100, 19.25.
    * Yesavage JE, Leirer VO, Denari M, Hollister LE (1985). Carry.over effects of marijuana intoxication on aircraR pilot performance: a preliminary report. American Journal of Psychiatry, 142, 1325.1329.
    * Young AM, Goudie AJ (1994). Adaptive processes regulating tolerance to behavioral effects of drugs. In: FE Bloom, DJ Kupfer (Eds.) Psychopharmacology: The Fourth Generation of Progress. Raven Press, New York.

~~Link to article

[Uzi578]

Marijuana & Alcohol Combined Increase Impairment

By: National Highway Traffic Safety Administration
Number 201, June 1999

[Erowid Note: One problem with this report is that it has an HTML / OCR error which seems to have lost the 'micro' character from in front of the grams, so the version we received included absurd doses. We changed the document to include "ug" (microgram) wherever there was just "g" for the concentration of THC in blood.]

Original URL: http://www.nhtsa.dot.gov/people/outreach/traftech/pub/tt201.html  [Note - Link Doesnt Work]
While alcohol is clearly the predominant drug in fatal crashes, marijuana is the next drug most frequently found in crash-involved drivers. Alcohol and marijuana are often found together (See Traffic Techs 57 and 62, 1993 and 1994).

The Institute for Human Psychopharmacology at Maastricht University in the Netherlands has completed the second of a series of studies for the National Highway Traffic Safety Administration (NHTSA) to assess the separate and combined effects of marijuana and alcohol on driving performance in real driving situations. Eighteen subjects between the ages of 20 and 28 who said they smoked marijuana and drank alcohol at least once a month participated in the study. They were all licensed drivers; half were males and half were females.

Each participant was dosed with marijuana alone, alcohol alone, a combination of marijuana and alcohol, or neither. There were two levels of 9-tetrahydrocannabinol (THC), the primary psychoactive ingredient of marijuana, tested: a low dose at THC 100 ug/kg body weight and a moderate dose at THC 200 ug/kg. A third, marijuana placebo, containing marijuana leaf from which the THC had been removed, was also run. These levels were selected based on an earlier NHTSA study. There were two levels of alcohol tested: an initial alcohol dose sufficient to achieve a blood alcohol concentration (BAC) of about 0.07 ug/dl and an alcohol-free placebo. Since alcohol concentration declines with time, booster doses of alcohol were given later in the test to sustain BACs around 0.04 ug/dl during testing, well below the per se levels in the United States.

There were two on-road test scenarios. The Road Tracking Test measured a driver's capability to maintain a constant speed of 62 mph (100 km/h) and a steady lateral position between the boundaries of the right traffic lane. The Car Following Test measured drivers' reaction times and headway variability (distance between vehicles) while driving 164 feet (50 m) behind a vehicle that executed a series of alternating accelerations and decelerations. On a given test evening after dark, participants smoked the marijuana or placebo, and drank the alcohol or placebo, and then waited 30 minutes to begin the driving tests. On a particular evening, they drove each of the two 25 mile long tests on real roads with real traffic twice (first and second repetitions), accompanied by a driving instructor with separate dual controls.

Deviations in Lateral Position

0 0 = no alcohol, no THC	A 0 = alcohol, no THC
0 T100 = no alcohol, THC 100 g/kg	A T100 = alcohol, THC 100 ug/kg
0 T200 = no alcohol, THC 200 ug/kg	A T200 = alcohol, THC 200 ug/kg

Lateral Position and Time Out of Lane

The graph above shows the average or mean deviation of lateral position during the Road Tracking Test. In practical terms, it's a measure of the composite index of allowed weaving, swerving, and overcorrecting. Failures to keep the vehicle within the boundaries of the lane are shown in the next graph, Time Out of Lane.

Both THC doses alone, and alcohol alone, significantly impaired performances on both road tests, compared with the baseline (no alcohol, no marijuana). Performance deficits were minor after alcohol and the low THC dose, and moderate after THC 200 ug/kg. Combining marijuana with alcohol, however, severely impaired performance, leading to decrements in performance as great as for driving with BACs at .09 and .14, respectively. These comparisons are based on previous research documenting alcohol-induced performance deficits. The percentage of the time a driver spent out of lane increased with the severity of drug effects, until arriving at 1.1 percent after the combination of alcohol and THC 200 ug/kg.



Reaction Time

The next graph shows how reaction times increased with each drug or alcohol dose, compared with the baseline (00). With neither THC nor alcohol, the mean reaction time was 4.65 seconds. This is the time it took for an unimpaired driver to begin to initiate a response. Reaction time increased to 6.33 seconds under the combined influence of alcohol and THC 200 ug/kg, a 36 percent performance decrement.

Considering that their vehicles were traveling at 59 mph at the time, this delay meant that the vehicle traveled, on average, an additional 139 feet beyond the point where the subjects began to decelerate. Even the lower THC dose, by itself, retarded the subjects' mean reaction time by 0.9 seconds.

Another measure was the average headway, or distance between the lead and following vehicles.



In every drug condition, there was a diminished ability to perceive and/or respond to changes in the relative velocities of other vehicles, and to adjust one's own vehicles' speed accordingly.

Conclusions

Marijuana, even in low to moderate doses, negatively affects driving performance in real situations. While previous research on alcohol effects alone show that alcohol at BACs around .10 is far more impairing than low or moderate THC doses alone, marijuana does impair driving performance. Drivers would be less than normally able to avoid collisions if confronted with the sudden need for evasive action. The effect of combining moderate doses of alcohol and moderate doses of marijuana resulted in a dramatic performance decrement and levels of impairment, as great as observed when at 0.14 BAC alone.

HOW TO ORDER

For a copy of Marijuana, Alcohol and Actual Driving Performance (39 pages), prepared by the Institute for Human Psychopharmacology, write to the Media and Marketing Division, NHTSA, NTS-21, 400 Seventh Street, S.W., Washington, DC 20590, or send a fax to (202) 493-2062.

U.S. Department
of Transportation
National Highway
Traffic Safety
Administration
400 Seventh Street, S.W. NTS-31
Washington, DC 20590

Traffic Tech is a publication to disseminate
information about traffic safety programs,
including evaluations, innovative programs,
and new publications. Feel free to copy it as you wish.
If you would like to receive a copy contact:
Linda Cosgrove, Ph.D., Editor, Evaluation Staff
Traffic Safety Programs
(202) 366-2759, fax (202) 366-7096
E-MAIL: lcosgrove@nhtsa.dot.gov

~~Link to article

[Uzi578]

Part 1 of 3

Cannabis and Road Safety: An Outline of the Research Studies to Examine the Effects of Cannabis on Driving Skills and on Actual Driving Performance

By: Dr G.B. Chesher
Department of Pharmacology University of Sydney and National Drug and Alcohol Research Centre University of New South Wales.

Dr Chesher provides an extensive coverage of the latest Australian and overseas research on the impairing effects on driving of cannabis, particularly relative to those of alcohol.

Contents:

1. Executive summary
2. Introduction
     2.1 Pharmacology and pharmacokinetics
     2.2 Behavioural pharmacology and psychology
3. Studies using the techniques of epidemiology
     3.1 Pharmacology and pharmacokinetics
     3.2 Pharmacokinetics
4. A comparison of the effects of alcohol and cannabis on skill performance and driving skills
     4.1 Laboratory tests
     4.2 Duration of cannabis-induced impairment in laboratory tests
     4.3 The effect on laboratory tasks of alcohol and cannabis in combination
     4.4 Driving simulators
     4.5 On-road driving
5. Epidemiology
     5.1 Questionnaire based surveys
     5.2 Incidence of drug detection in crash involved drivers
     5.3 Attempts to assess whether or not the driver who has detectable drugs in the blood stream was culpable in the accident
6. The use of 'Responsibility Analysis' or estimation of 'culpability' to determine the role of drugs in crashes
7. Alcohol and cannabis in epidemiological studies
8. Summary (of the evidence presented above)

1. EXECUTIVE SUMMARY

There is no doubt that cannabis, smoked or taken by mouth produces a dose-related deficit in tests of performance skills as conducted in a laboratory.

Using driving simulators and on-road real vehicles, cannabis has been shown to affect driving performance. However, the effects are less severe than would be anticipated from the evidence obtained from the laboratory studies of individual tests of skills performance.

A description is given of epidemiological studies to determine the role of cannabis in road crashes. The pharmacological problems associated with these studies are described. The results of studies within the last 10 years have failed to present clear evidence for a role of cannabis in road crashes. The role of alcohol in all studies has proved to be dominant.

The evidence indicates that there is a clear difference in the mode of action of cannabis and alcohol, both pharmacological and behavioural and this is presented and the implications described.

The most recent of studies of cannabis and driving (Robbe & O'Hanlon, 1993), which was sponsored by the U.S. National Highway Safety Traffic Administration included a review of the literature. The authors' comments in summary of their literature review and of their own results include the following:

The foremost impression one gains from reviewing the literature is that no clear relationship has ever been demonstrated between marijuana smoking and either seriously impaired driving performance or the risk of accident involvement. The epidemiological evidence, as limited as it is, shows that the combination of THC and alcohol is over-represented in injured and dead drivers and more so in those who actually caused the accidents to occur. Yet there is little if any evidence to indicate that drivers who have used marijuana alone are any more likely to cause serious accidents than drug free drivers.

Of the many psychotropic drugs, licit and illicit, that are available and used by people who subsequently drive, marijuana may well be among the least harmful. Campaigns to discourage the use of marijuana by drivers are certainly warranted. But concentrating a campaign on marijuana alone may not be in proportion to the safety problem it causes.

2. INTRODUCTION

In this paper I will examine briefly the studies which have sought an understanding of the effect of cannabis and of alcohol on driving skills and their role in road crashes. This information has been based upon scientific data which have been collected from several scientific disciplines. I have outlined these in earlier papers and will only mention them briefly here.
The major purpose of this paper is to compare the two drugs, alcohol and cannabis and the status of the evidence as to their role in road crashes.
The determination of the legal limit for alcohol has been achieved in a scientific manner. There are pharmacological reasons why it has not been possible to follow these same techniques with drugs other than alcohol, including cannabis. This paper will draw attention to these problems.
First, we might briefly outline the nature of the evidence which has been generated to examine the effects of cannabis on driving skills and as a causative factor in road crashes. This information has been derived from the employment of three scientific disciplines:

2.1 Pharmacology and pharmacokinetics

Pharmacology is the study of the way a drug exerts its action in the body. This involves an understanding of the sites and the body systems where the drug acts and the consequences of this drug-system interaction. Information obtained from these studies can help to formulate an hypothesis as to how the drug may influence driving behaviour.
The pharmacological discipline known as pharmacokinetics studies the fate of the drug after it has been taken. It provides information as to the rate of absorption from the site of administration; the manner of its distribution in the body up to the delivery to its site of action (eg. the brain). Pharmacokinetics also studies the way the body eliminates the drug from the body and includes the understanding of the metabolism and excretion of the drug.

2..2 Behavioural pharmacology and psychology

These involve studies of the effects of the drug on human behaviour. The behaviour of relevance to this discussion concerns those skills which are (or are related to) those necessary for the safe control of a motor vehicle or other items of machinery. Psychological studies also involve the effects of the drug on mood and cognition.

The three classifications of these studies are:
(i) Those performed on specific tests of behaviour or psychological functioning (for example, tests of reaction times of various degrees of complexity; tracking; divided attention or vigilance);
(ii) Those performed in a driving simulator; and
(iii) Those performed in a real car, either in a closed course or in real traffic.

3.  STUDIES USING THE TECHNIQUES OF EPIDEMIOLOGY

These studies aim to determine whether or not a causal relationship between drug use and a motor vehicle crash exists.
I shall look at each of the above factors and will compare the two drugs alcohol and cannabis in the light of current evidence. In interests of time and space I have in this summary referred to reviews of the literature and have made only a brief description of the studies themselves. A fuller description of these can of course be sourced from the original literature of the cited reviews.

3.1 Pharmacology

First, the drugs themselves. With the increase in pharmacological knowledge it is known that most drugs act upon specific receptors. A receptor is a specific site in tissues, frequently on the cell membrane, which has a specific structural affinity (shape) for a naturally occurring molecule. The interaction between receptor and the endogenous molecule is part of the body's normal, physiological functioning. Most drugs exert their activity by acting upon these receptors. Examples of such drug-receptor interactions are the opioids (morphine etc) and the opioid receptors; the antihistamines and the histamine receptors and the benzodiazepines which act on the benzodiazepine receptors. The endogenous substances that physiologically act on these receptors are, respectively, the endorphins and enkephalins on the opioid receptors; histamine on the histamine receptors; however the identification of the physiological substance for the benzodiazepine receptor has yet to be identified.

Research within the last five years has revealed that the cannabinoids, such as delta-9-tetrahydrocannabinol (THC) from the cannabis plant exert their effects on specific receptors known as the cannabinoid receptors. To date two cannabinoid receptors have been described and an endogenous (physiological) substance has been identified. This has been given the name 'anandamide'. It is very likely that in the near future more cannabinoid receptors will be described and more endogenous substances that act on these receptors will be identified. An historical overview of these findings has recently been published.

In contrast, the evidence strongly indicates that the drug alcohol does not act on a specific receptor, but acts more widely in a non-specific manner on the cell membranes themselves. This understanding is supported by the evidence that alcohol exerts effects on most of the tissues of the body and in excess is toxic to most tissues. The reader is referred to a recent review on this subject by Dufor and Caces.

Drugs which act upon a specific receptor produce their effects in doses measured usually as nanograms or micrograms per kilogram of body weight. Alcohol doses are measured in grams per kilogram - many hundreds of thousands times greater than those of most other drugs. Alcohol is a very non-specific drug.

Another important factor is that receptor-specific drugs exert their activity only on those cells which bear the specific receptor. In the case of the cannabinoids these receptors are found only in the brain in the basal ganglia, the cerebellum, the brain stem, thalamic nuclei, hypothalamus and corpus callosum. On the other hand alcohol affects all nerve cells to which it is delivered by the circulating blood.

Consequently it is not surprising that differences in the action of alcohol and the cannabinoids have been described in their effects on mood and behaviour. These will be discussed below.

3.2 Pharmacokinetics

The pharmacokinetics of alcohol and the cannabinoids could hardly be more different.

The apparent volume of distribution of alcohol (the volume of fluid in which the drug seems to be dissolved throughout the body) is quite low, consisting of the 41 litres of body water, providing a value of about 0.59 litres/kg. Cannabinoids, on the other hand, are very fat soluble and have a high volume of distribution which has been estimated to be about 10 litres/kg.

The meaning of these values is that the concentration of alcohol in the blood provides a reliable estimate of the concentration of the drug in the brain. This in turn provides a reliable estimate of the degree of impairment of the drinker. In addition to this, alcohol is excreted via the lungs to the breath and the blood : breath ratio is such that the determination of the alcohol in breath provides a reliable estimate of the blood alcohol concentration. It is because of these pharmacokinetic properties of alcohol that it has been possible to accumulate the epidemiological data upon which our drink-driving laws have been based.
Cannabinoids, on the other hand are lipophilic (fat loving) and are distributed in the fatty tissues of the body. When smoked, which is the most common route of administration, the cannabinoids are rapidly absorbed from the lungs into the bloodstream. Being so fat soluble the cannabinoids readily cross membranes, leave the circulation and are rapidly 'dumped' into various tissues of the body, including the brain. In this way the concentration of cannabinoid in the blood declines very rapidly as indicated in Fig 1. [Note - None of the Figure1/Fig1 links work so I did not link them]

As indicated in the Figure, we can describe the concentration of cannabinoid across time in the blood in the three phases: absorption, re-distribution and elimination. The steep upward curve of THC represents the inhaled THC being absorbed into the blood through the lungs; the equally sudden drop in the concentration of THC represents the drug being 'dumped' from the bloodstream into fatty tissues. This redistribution phase 'flattens' out as the 'dumped' THC re-enters the blood and is then metabolised in the liver-the elimination phase. It is important to note that the sudden decline in the concentration of THC (the psychologically active cannabinoid) in the blood does not represent drug metabolism but rather the rapid re-distribution of the drug from the blood into other tissues. The metabolism of the cannabinoids takes place when these 'dumped' cannabinoids are released back into the bloodstream whence they pass through the liver and are very rapidly metabolised and subsequently excreted.

Figure 1. The blood concentration of THC (squares) and its inactive metabolite, carboxy THC (THC Acid; diamonds) after the smoking of a marijuana cigarette. Each point is the mean of results from six volunteers, all of whom were free from cannabinoids before smoking the drug. [The 925±7mg refers to the average weight of the cigarettes and the 1.32% refers to the dry weight concentration of THC]

Figure 1 also shows the blood picture of the inactive metabolite, carboxy THC (or THC acid). It is important to note several points about the pharmacokinetics of this substance. First, in the study indicated here (Fig 1) all of the volunteers had no cannabinoids in their blood before they began smoking. Second, the THC acid is formed in the liver from the metabolism of THC, therefore its appearance in blood follows that of the parent, THC. Third, the THC acid concentration then increases and surpasses that of the parent molecule in the blood. At a time when the parent THC is in the blood at only a very low concentration, that of the metabolite is higher and exists in the blood for a longer time. Therefore, should the smoker smoke again before the parent molecule and its metabolite have been eliminated, the ratio of the concentrations of THC and of the THC acid will be different from that shown in Figure 1. This is because there will exist a higher concentration of the metabolite than of the THC in blood at the time when the next dose of cannabis is smoked.
For this reason, analytical data that provides a value only for the metabolite can only be validly interpreted as indicating recent consumption of cannabis; however the time of this consumption could be a matter of hours or days. For this reason the quantitative determination of only the metabolite is of no value to determine possible impairment.

To assess possible impairment the analyst must provide data for the active molecule, THC. And when this occurs, the only interpretation possible on present knowledge is to infer the recent consumption of the drug by smoking. To date no meaningful correlation between blood concentration of THC and impairment in laboratory tasks has been established. This point will be clarified when the results of the recent epidemiological studies are discussed below.

Yet another problem arises in the interpretation of blood concentrations of cannabinoids. The pharmacokinetics of the cannabinoids are quite different when the drug is taken by mouth. Space in this discussion precludes further discussion of the pharmacokinetics after oral administration, but suffice to say the absorption of cannabinoids taken orally is slow and erratic. The absorbed THC passes through the liver and is rapidly metabolised. This results in a different proportion of THC to the metabolite, THC acid than encountered after smoking. There is a greater amount of entero-hepatic 'recycling' as some of the cannabinoids are stored in the bile in the gall bladder. These cannabinoids can later be 'recycled' and reabsorbed into the bloodstream when the gall bladder empties. In this country, most who use cannabis, smoke it.

It is also important to note that the detection of cannabinoids in a urine sample provide evidence only that the donor of that urine has been exposed to cannabis at some time in the past. It gives no indication at all of impairment or of intoxication. A frequent, heavy cannabis user may be excreting cannabinoids in urine for some weeks or in some cases, for more than a month. Those who take the drug by mouth also will be excreting the drug for a longer period.

4. A COMPARISON OF THE EFFECTS OF ALCOHOL AND CANNABIS ON SKILLS PERFORMANCE AND DRIVING SKILLS

4.1 Laboratory tests

Laboratory tests isolate specific psychological functions and determine the skill of the test subject on that function. Most studies test each volunteer on each test before and after taking the drug. For testing alcohol and cannabis, the choice of these tests rests upon an assessment of their relationship to the task of driving a motor vehicle. However, the fact is that no battery of separate tests comprehensively defines the actual task of driving. In fact, Joscelyn and others (Joscelyn et al., 1980) examined the plethora of methods employed in these studies and commented:

... many tests routinely employed have limited validity or no demonstrable relation to real-world driving. Measuring the 'same' behaviors often differ, raising questions about the comparability of experimental findings.

Laboratory tests, nevertheless do provide a 'screening' of the potential for drugs to impair specific behaviours. However, results from such laboratory testing should not form the sole basis for any judgement of the potential of a drug to impair actual driving skills or to increase the probability of an accident. For this reason, evidence for the traffic hazard associated with any drug should be confirmed by studies of actual driving (either using driving simulators or a real car) and by studies using epidemiological methods.

The data from laboratory testing of alcohol has been reviewed by Moskowitz and Austin and of the effects of cannabis by Klonoff, Moskowitz, and by Chesher. It is clear that both alcohol and cannabis cause dose-dependent deficits in the performance of specific laboratory tasks.

It is to be noted that the doses of cannabinoids in these tests are lower than those in use by many smokers of cannabis today. However, they may have been appropriate to the cannabis experience of the volunteers when these studies were conducted. In many of these studies, the volunteers were asked to rate the effect of the dose given with that of their general experience with the drug. In many (but not all) cases the doses given produced subjective effects which were as great as those generally experienced by the volunteers in their social use of the drug.

Looking at the Australian studies across time, from the 1970s to the 1990s these observations are in accord with the results expressed in a recent publication concerning the patterns of cannabis use in Australia. The earlier studies produced deficits in testing which were greater than those in the later studies. The data presented by Donnelly and Hall (1994) indicate that:

The prevalence of cannabis use seems to have been very low by contemporary standards in the early 1970s. It increased substantially throughout the 1970s and 1980s, levelled off in the late 1980s, and has probably shown a small increase in the early 1990s.

The phenomenon of tolerance to cannabis is well established and this in turn is a serious confounding variable in the studies with this drug. Tolerance develops with the regular and frequent use. This in turn depends upon the pattern of use of those in the study sample. The correlation of performance : dose : and tolerance requires further study. There is very little information available as to the change in doses used across the years since the 1970s as most data refer only to frequency of use. Studies involving high doses of cannabis should be undertaken, but with due consideration given to the degree of tolerance of the volunteers to be studied.

The Australian data presented by Donnelly and Hall indicate that:

Most cannabis use is infrequent and intermittent, with about three-quarters of adult women and two-thirds of adult men having discontinued their use, or continued to use less often than weekly. The proportion of users who are weekly users is highest in the younger age groups. Rates of weekly and lifetime use are highest among those aged 20 to 24 years, and decline markedly with increasing age.

4.2 Duration of cannabis-induced impairment in laboratory tests.

Most studies have reported a duration of cannabis-induced impairment of the order of 4 hours. On the other hand there have been three studies which have reported a longer duration of cannabis effects of between 10 to 24 hours. However, these reports have been questioned for methodological or reasons of interpretation. That of Yesavage et al. did not include a control group. Subsequently the study was repeated by Leirer et al. in an attempt to replicate this effect using a control group but was only able to show an effect up to four hours after smoking (ie. that described in the many other studies of this effect). A third study, also with a control group, did demonstrate an effect at 24 hours after smoking. The statistical significance of the effect required a statistical procedure (one tail 't' test) which is of questionable validity when there was no previous statistical proof that the effect was expected. This means that the effect was at best, only marginally significant. The study by Moskowitz et al, as described in Moskowitz's 1985 review (Moskowitz, 1985) was of a:

.... compensatory tracking task performed while simultaneously executing a visual search task as well as a critical tracking task. Performance was significantly impaired on the compensatory tracking task for more than 2 hours and upon the critical tracking task for up to 10 hours, albeit, intermittently during the period from 4 hours on. [emphasis added]

At present I think it is fair to conclude that the evidence for the long duration of cannabis induced impairment requires more study to confirm its validity. Furthermore, both tasks in which it was described are very difficult tasks. It has been argued that the use of cannabis by pilots in the 24 hours preceding flying may be more an indicator of poor judgement rather than a cause for concern about the residual psychomotor effects of cannabis. 

4.3 The effect on laboratory tasks of alcohol and cannabis in combination

The effect of this drug combination has been reviewed and only an outline will be given here.

There is very clear evidence from numerous studies of the effect of alcohol and of cannabis on the performance of specific tasks in the laboratory. Both drugs produce a dose related impairment on these tasks and the effect of the drugs when given in combination is essentially additive. Although of more academic than practical interest is the evidence as to the nature of this additivity. Several studies have observed a trend that the effect of cannabis plus alcohol is less than additive, meaning that 1 + 1 is less than 2. In the most recent study, Dauncey et al. reported this effect, found to be statistically significant, and termed it to be a 'de-intensification'. In the light of the present knowledge of the quite different mode of action of cannabis and alcohol such an interaction is not necessarily surprising.

What is quite surprising and important however, is the result of a study by Perez-Reyes. For pharmacological reasons the researchers studying the alcohol-cannabis interaction administered the drugs such that the peak of blood concentration of both drugs occurred as near as possible at the same time. Such is the thinking of the pharmacologist! Indeed Perez-Reyes and his colleagues had reported such a study showing an additive decremental effect of the drug combination. Interestingly, in their later study they had the volunteers smoke marijuana (placebo; 1.7% and 3.58% THC) before they commenced drinking alcohol (0.85g/kg) over a period of 30 mins. This would have produced a BAC of the order of 0.1g%. Their results showed a dose-dependent effect for cannabis and the characteristic effects expected for the one dose of alcohol. However, no significant interaction between the two drugs was recorded. The authors concluded:

The lack of interactive effects, particularly on psychomotor performance, highlights the influence that the order of administration of the companion drug has on its interaction with the reference drug.

4.4 Driving simulators

A driving simulator is also a laboratory based apparatus. It is important to realise that it is only a simulation of real life driving and driving simulators vary greatly in the degree to which they can simulate the real event. It is fair to say that all but the most sophisticated and extremely expensive simulators are to the test subject, still a laboratory piece of equipment. They lack realism both in the dynamics of car driving and in the visual presentation of the road and other traffic. Nevertheless they are able to present simulated dangerous presentations to which the driver must respond. The effects of cannabis on performance in a driving simulator have been reviewed and a summary only is given here.

The early driving simulator studies, for the driver, were not interactive with the 'driving scenery' which was generally a film of the road to be covered and the driver had little or no control over the presented imagery.ÊÊ These studies showed no significant effects of marijuana on car control. However marijuana did produce the following effects, namely:

(a) An increase in decision latency before starting, stopping or overtaking;
(b) Impaired monitoring of a speedometer; and
(c) Reduced risk-taking behaviour in tasks requiring a decision to overtake a vehicle in the presence of an oncoming car.

Later simulator studies with apparatus with a more realistic driving dynamics and an interaction between 'scenery' and the driving manoeuvres did show marijuana effects on car control. The study by Smiley et al. found that cannabis increased lateral position variability, headway variability, and caused the 'driver' to miss more signs that indicated the need to follow another route. On the other hand, cannabis caused the subjects to drive in a more conservative manner inasmuch as they maintained a longer headway when car following, refused more opportunities to overtake a vehicle in front and when they accepted this opportunity, they began to do so at a greater distance from the approaching vehicle. The effects of alcohol (at about 0.08g% BAC) in this study were surprisingly small.

Another and very similar study by Stein et al. showed alcohol effects were as one would expect and significantly affected practically every performance parameter. Alcohol (at about 0.1g% BAC) was associated with significantly increased 'accidents' (hitting obstacles or exceeding road edges by a full car width) and 'traffic tickets' (exceeding speed limit by 32 'radar checks'). Alcohol was also associated with increased lane deviations, speed variability, response times to signs, and errors in sign recognition. In contrast, cannabis was associated with few changes. The mean speed travelled was lower and two measures of steering control changed significantly. Alcohol and cannabis in combination were associated with more adverse reactions than alcohol alone. Alcohol was consumed first and the performance testing was begun 15 minutes after the end of cannabis smoking.

~~Link to outline

[Uzi578]

Part 2 of 3

4.5 On-road driving

Driving studies with a real car, conducted in an open field, of course present a more realistic experience of a motor vehicle than do simulators. However they usually require the driver to undertake manoeuvres that are not necessarily part of normal driving - such as weaving between cones. Those studies undertaken in on-road traffic naturally require great care on the part of the experimenter to avoid dangerous driving. Therefore these studies are restricted in the measures that can be realistically taken. They are somewhat akin, for both the experimenter and the test driver, to a driver undertaking a test for a driving licence. Indeed, experimental studies of the effects of drugs using in-car performance have been described by Smiley as being really a simulation of real driving.

On-road driving studies vary considerably in their experimental design and in the tests of driving employed. In this paper, only the broadest outline of the results is given in the interests of brevity. Reviews of these studies have been presented and published. The reader is referred to the original studies or to the cited reviews for more information.

There have been to date, seven on-road studies to examine the effects of cannabis on driving performance. Each of these is outlined below:

1.  Klonoff studied volunteers in a closed course as well as in-traffic on a city road. The closed course study comprised eight tests and the response scores rested essentially on the number of cones struck. Testing was conducted in 4 blocks, each of 5 trials. The first three were taken as practice and the fourth, after drug treatment, were the test trials. The anticipated scores in the fourth block were determined by regression analysis on the assumption that the rate of learning or performance would continue at the same rate. Using this technique the author concluded that there was an impairment under cannabis. While the mean of the impairment was not large, the trend was clear.

 The city traffic study was conducted rather in the manner of a driving test by a driving examiner. The subjects drove for about 45 minutes on a course of 16.8 miles after being given their dose of cannabis. A strong trend towards impaired performance was indicated by the lower scores given by the examiner on judgement and concentration after the higher dose of cannabis.

2.  Hansteen et al. conducted a closed course study in which subjects were required to drive six times around a 1.1 mile course set out on an airfield. The course was set out with cones and poles and the number of these hit were counted. The course involved curves and straight sections and drivers were required to undertake various manoeuvres. The mean number of struck objects per lap increased from a mean of 13.2 in the placebo condition, 13.4 in the low cannabis dose, 16.8 for the high cannabis and 17.4 for the alcohol dose (BAC 0.07g%). The effects for the high cannabis dose and the alcohol dose achieved significance.

3. Casswell conducted a closed course study in which the behaviours sampled were more typical of those for real driving, than for the studies outlined above. Driving behaviours recorded included overtaking, responding to road signs, making a hairpin turn and driving through a narrow gap. A subsidiary reaction time task was also included to monitor attention. Driving behaviour under cannabis, alcohol and the combination was tested. After alcohol, and alcohol plus cannabis, the subjects showed poorer tracking performance and drove at increased speed over various segments of the course, including the hairpin bend, and the straight section. Under alcohol alone, the speed through the narrow gap was also increased.

 On the other hand, marijuana alone was not accompanied by steering or tracking errors. The mean speed dropped significantly after cannabis, both on the hairpin bend and on the straight section of the course.

Casswell suggested that drivers under the influence of cannabis appeared to compensate for what they perceived as being an adverse effect on driving. Compensation was exhibited by driving more slowly. This contrasted with the effects of alcohol. The increased reaction times to the subsidiary task under cannabis suggests an effect on attention. The extent of this effect was of the same order as that measured by the author in another study after 8 hours of continuous driving.

4. Attwood conducted a study on a closed course constructed on an airfield and, like Casswell, used measures appropriate to real driving including acceleration, following a lead car which varied its speed and responding to 'traffic signals'. The drug effects (alcohol, and two doses of cannabis alone and together with alcohol) recorded were not particularly robust, even with a complicated multivariate analysis which did distinguish the treatment conditions from each other.

5. The study by Peck and colleagues (Peck et al., 1986) from the California Department of Motor Vehicles, is best summarised by the authors' own summary.

Approximately 80 volunteer male marijuana and alcohol users received one of four experimental treatments: (1) marijuana, (2) alcohol, (3) marijuana and alcohol, or (4) double placebo.

After consumption, each subject drove a vehicle over a test course which simulated a number of real-world driving conditions.

Four post-drug runs were involved, separated by one hour intervals. The subject's performance was rated by an in-car examiner, outside observers, and computerised vehicle measurements.

Blood and urine specimens were extracted after each run to establish levels of tetrahydrocannabinol (THC), serum carboxy, and alcohol. A variety of multivariate statistical techniques were applied in evaluating treatment effects.

Both marijuana and alcohol had significant effects on driving performance, and the effects were particularly detrimental under the both-drugs treatment. The effects of marijuana were more rapid than those of alcohol and somewhat less severe for most tasks.

 In this study cannabis was smoked after the consumption of the alcohol dose. In discussing their results and comparing them with other studies, they had this to say:

There is a vast amount of empirical evidence documenting the effects of marijuana on a wide array of human performance measures-cognitive, psychomotor and affective. Although the literature has clearly established that marijuana affects all three domains and results in detriments in the ability to perform many psychomotor and cognitive tasks, the evidence is somewhat more equivocal on the question of actual driving skill and even more equivocal on the question of those aspects of driving skill that are related to safety and accident avoidance. [Emphasis that of Peck et al.]

6. Smiley et al. tested the effects of cannabis (placebo and two doses) and alcohol (placebo and BAC of 0.05 g%) in combination and the effect of alcohol alone (BAC 0.08g%) on driving in a closed course study using an instrumented car.

The high dose of cannabis significantly increased headway and headway variability (ie distance from a car in front). Alcohol alone at the BAC 0.05g% produced an increase in speed, both in the straight sections of the road and in curves. In her review of her own study, and those of others, Smiley (Smiley, 1986) concluded:

In conclusion, marijuana does appear to impair driving behaviour. However, this impairment is mediated in that subjects under marijuana treatment appear to perceive that they are indeed impaired. When they can compensate, they do, for example, by not overtaking, by slowing down and by focussing their attention when they know a response will be required. Unfortunately, such compensation is not possible where events are unexpected or where continuous attention is required. Effects on driving behaviour are present shortly after smoking but do not continue for extended periods. [emphasis added]

7. The most recent and most comprehensive study of the effect of cannabis on driving on city roads and a public highway is that conducted in The Netherlands and was sponsored by the U.S. National Highway Safety Traffic Administration. An intelligent departure in methodology in this study from the others reviewed here is that the dose of cannabis used was determined in a pilot study using the volunteers who were to take part in the main study. The aim was to estimate the dose these volunteers generally use on a social occasion. Accordingly socially appropriate doses (for these subjects) were chosen for the driving study. Three driving studies were then performed. The first was conducted on a closed section of a public highway with no traffic; the second on a highway with traffic and the third in city traffic. The measure they have found to be of significance is the standard deviation of lateral position on the roadway (SDLP). It is a measure of the 'automatic' function of information processing in the driving task. Cannabis, in all tests produced a dose-related increase in the SDLP. Mean speed was somewhat reduced under cannabis as was the headway distance from the lead vehicle in the test in highway traffic.

The test under city driving conditions was conducted under one dose of cannabis and as a comparison, subjects were also tested under alcohol at a BAC of 0.04g%. Results in this test showed that this modest dose of alcohol, but not cannabis, produced a significant impairment of driving performance relative to placebo. Alcohol impaired driving performance but subjects did not perceive it. Cannabis did not impair driving performance yet the subjects thought it had. After alcohol, there was a tendency towards faster driving and after cannabis, slower.

This research group has conducted many studies with the same methodology and has accumulated much data on the effects of other drugs. They therefore were able to indicate the extent of the impairment on the measure of SDLP. The greatest effects of cannabis in this study were 3.7 and 2.9cm. In other studies drugs, for example diazepam (Valium), or lorazepam (Ativan), produced increases of 7 and 10cm respectively. The authors commented:

In so far as its effects on SDLP are concerned THC was just another moderately impairing drug.

The authors go on to say that the effects of cannabis differ qualitatively from those of other depressant drugs, especially alcohol:

Very importantly our city driving study showed that drivers who drank alcohol overestimated their performance quality whereas those who smoked marijuana underestimated it. Perhaps as a consequence, the former invested no special effort for accomplishing the task whereas the latter did, and successfully. This evidence strongly suggests that alcohol encourages risky driving whereas THC encourages greater caution, at least in experiments.

Finally, Robbe contrasted the effects of cannabis when measured with laboratory based, individual tests in the laboratory, with those conducted in an on-road vehicle:

The results of these studies corroborate those of previous driving simulator and closed-course tests by indicating that THC in single inhaled doses up to 300 µg/kg has significant, yet not dramatic, dose-related impairing effects on driving performance. They contrast with results from many laboratory tests, reviewed by Moskowitz (1985), which show that even low doses of THC impair skills deemed to be important for driving, such as perception, coordination, tracking and vigilance. The present studies also demonstrated that marijuana can have greater effects in laboratory than driving tests. The last study, for example showed a highly significant effect of THC on hand unsteadiness but not on driving in urban traffic.

5. EPIDEMIOLOGY

The studies outlined above indicate that cannabis does cause dose-dependent effects on laboratory based tests of human skills. Furthermore, studies utilising driving simulators and on-road driving also indicate a degree of cannabis induced impairment of driving skills. However in these cases the extent of the impairment indicated from laboratory studies is not replicated in the simulator or in-car studies.

The effects of alcohol on the other hand can be demonstrated both in laboratory studies and in simulated or on-road driving at very much the same dose levels. Explanations for these differences between alcohol and cannabis have been suggested and rest essentially upon the difference in the awareness by the drug taker of the presence of drug impairment. This in turn may be explained by the present understanding of the quite different ways alcohol and cannabis are known to act on the brain.

Also mentioned above and in other publications our present laws on alcohol and driving have been based upon the scientific principles outlined here and in particular on the results of epidemiological studies. It is pertinent therefore to discuss briefly the nature of the epidemiological studies undertaken to date with cannabis and road crashes.

Epidemiological studies with alcohol are greatly facilitated by the pharmacokinetics of that drug. Alcohol is excreted in the breath and the ratio of the concentration on the breath and in the blood is relatively constant. Therefore the determination of the concentration of alcohol in the breath (by a 'breathalyser') provides a reasonably and acceptably accurate indication of the blood concentration. It is unfortunate therefore that cannabinoids are not excreted on the breath and the concentration of cannabinoids that can be detected on breath represent only that contained in the 'dead-space air' in the upper respiratory tract. The cannabinoids so detected do not correlate in any way with the blood concentration. In addition to this the blood concentration of cannabinoids do not show any useful relationship to the degree of impairment or the degree of subjective effects of the drug. The blood concentration of alcohol on the other hand does exhibit a reasonable correlation with the degree of impairment.

These properties of cannabis mean that the determination of the role of cannabis in road crashes by the same techniques of the case-control study as used for alcohol, is not an easy task. The pharmacokinetics of cannabis make this an exceedingly difficult task. The difficulty is not only related to the poor correlation between blood concentration and impairment, but also because it requires the collection of a blood sample-from both the crash case and the controls. The collection of the latter sample is likely to involve a high refusal rate, and this alone would almost certainly invalidate the study. One does not know the reason for the refusal!

The studies that have been undertaken to date can be described within three groups and these are:

(i) Questionnaire based surveys;
(ii) Incidence of drug detection in accident involved drivers; and
(iii) Attempts to assess whether or not the driver who has detectable drug in bloodstream was culpable in the accident.

Studies along the lines outlined above have been reviewed by Simpson.

5.1 Questionnaire based surveys

Questionnaire based surveys by definition depend upon self report data and their reliability is questionable. Furthermore, the incidence of cannabis use and the likelihood of a driver admitting to such use is likely to change across time.

5.2 Incidence of drug detection in crash involved drivers

This technique involves the analysis of blood or urine samples taken from crash involved drivers. The detection of cannabinoids in urine provides information only that the drug has been consumed within the last day or even month. It provides no indication at all of impairment. Therefore only the analysis of a blood sample is likely to be helpful. However, the detection of cannabis in a blood sample does not itself prove impairment or crash culpability. This fact has been well expressed by Compton as follows:

Knowing only the frequency with which crash-involved drivers use drugs does not allow one to know the danger posed by the drugs. It may simply reflect the general drug usage pattern in the driving public at large. For example, finding that 30% of crash-involved drivers have nicotine in their blood does not imply that nicotine was involved in the occurrence of their crashes. It may be that 30% of the general driving population smokes cigarettes and the smoking of cigarettes is unrelated to crash occurrence. Finding that a drug was overrepresented in crash-involved drivers (as compared to non-crash involved drivers) would strongly suggest it played a role in increasing crash risk. However, this approach requires knowing the drug usage rate of the general driving public, something we do not know and can not easily determine.

Furthermore, any comparisons of the incidence of cannabis detections in crash-involved drivers with those of non-crash involved drivers should be collected from a comparable population and at the same time. The patterns of cannabis use vary not only across time but also across populations.

Therefore studies reporting the incidence of drugs in the blood of crash-involved drivers is essentially meaningless without some control of the incidence of drug use in non-crash involved drivers. Nevertheless, such studies have been reported and are reviewed by Simpson who summarised that:

    * Marijuana users are certainly among drivers who are injured in road crashes (suggested by the presence of cannabinoids in urine);
    * More importantly, recent use, as indexed by the presence of THC in blood, is evident in perhaps less than 10% of injured drivers; and
    * When cannabis is detected, there is an 80% chance that alcohol will also be found.

5.3 Attempts to assess whether or not the driver who has detectable drugs in the bloodstream was culpable in the accident

Of the first attempts to assess culpability has been an ongoing series of data collected by McBay of fatal, single vehicle crashes. Culpability in single vehicle crashes is assumed to be that of the driver (assuming no mechanical fault can be found) and the choice of fatal crashes assumes that death occurred shortly after the accident; meaning that drug metabolism ceased at death and therefore the blood sample from the dead body will represent the blood picture at the time of the crash. Cannabis was detected in 7.8% of 600 such cases, but 88% of these also contained alcohol in concentrations which of themselves could have accounted for the crash.

6. THE USE OF 'RESPONSIBILITY ANALYSIS' OR ESTIMATION OF 'CULPABILITY' TO DETERMINE THE ROLE OF DRUGS IN) CRASHES

In the absence of a separate control group (as used in the assessment of crash probability with alcohol as described above) an alternative of a 'culpability index' is currently being employed in drug studies. The basic construct is first to formulate a means of determining the responsibility or culpability of a driver involved in a crash. There have been several means of constructing this 'culpability index' and this must be done with each of the accident cases by observers who have no information as to the drug status of each driver. The responsibility (or culpability) ratio is then determined as the proportion of drug-bearing drivers who were determined to be culpable, to the non-drug bearing drivers who were deemed to be culpable. The null hypothesis predicts a culpability ratio of 1.00 (ie, the drug has had no causal relationship with crashes).

To date there have been six studies employing this technique (two of which have involved the re-analysis of earlier generated data). These are briefly outlined below:

1. Warren and others re-analysed the data of Cimbura and found a culpability index for cannabis of 1.7, the same as that found for alcohol. However, the original data comprised a total of 484 drivers and pedestrians, 3.7% of whom were positive for cannabis. However, 88% of these people were also positive for alcohol. This left a very small number from which to assess a culpability ratio for cannabis alone.

2. Terhune also has previously collected data independently re-analysed to estimate a culpability ratio. All BACs over 0.10% were judged significantly more culpable than the drug-free group. The cannabis group also had a higher culpability ratio than the drug-free group, but this was only marginally significant (58.8% vs 34.4%). This estimation was also compromised by the small sample size for cannabis only (n=17). The cannabis plus alcohol group was analysed separately.

3. Donelson began a very ambitious project but was unfortunately thwarted by funding problems which precluded the complete analysis of the collected data. However, a random sample of 415 cases was analysed. The results cautiously suggested a finding consistent with those of Warren et al. and Terhune above.

4. Williams et al. in a study involving 440 cases, demonstrated as in the above studies that alcohol had a higher culpability ratio compared with culpable drug-free drivers (92% vs 71%). However, those drivers in whom only cannabis was detected were less likely to be responsible for the crashes (53% vs 71%).

5. Terhune et al. reported a very comprehensive study involving 1 882 cases. They found that alcohol was the dominant drug in fatal crashes, although the basic focus of their research was to describe the effect of drugs other than alcohol. They reported that fully 40% of the drivers had only alcohol in their systems and another 11% had alcohol combined with drugs. Among the drivers with BACs at or above 0.10% (n=625) their responsibility rate:

... was an extraordinary 94%, well above that found for any other single substance.

Of cannabis, the authors stated that while cannabinoids were detected in 7% of the drivers, the psychoactive agent THC was found in only 4%. Of the drivers with only one substance in their system, only 1.1% had cannabis alone, either as the THC the psychoactive compound or had the inactive metabolite carboxy THC. The presence of the inactive metabolite and the absence of detectable THC infers less recent ingestion of cannabisÑassuming an efficient analysis.

The THC only drivers had a responsibility rate below that of the drug-free driversÑie. as with the study by Williams et al. (1985) they were considered to be less likely to have been a cause of the crash than the drug-free drivers.

The report also indicated the range of THC concentrations found in the blood. There were 109 cases of THC alone; of these, 22.9% contained what the authors called a 'trace' ie. 1 to 2 nanograms THC per millilitre of blood (ng/ml); 69.7% contained 'low' concentrations between 3 to 19 ng/ml; and 7.3% contained a 'high' concentration of equal to or greater than 20 ng/ml.

~~Link to outline

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Part 3 of 3

6. THE USE OF 'RESPONSIBILITY ANALYSIS' OR ESTIMATION OF 'CULPABILITY' TO DETERMINE THE ROLE OF DRUGS IN) CRASHES

As with other studies, the dominant drug was alcohol, being found overall in 36% of all driver fatalities, 33% of which were over the legal limit of 0.05g%. Cannabis was found in 11% of cases of which 56% (n= 63) also contained alcohol (mean BAC 0.16 g% ± 0.08g%). There was no significant difference in the BAC of the alcohol only drivers and those with alcohol plus cannabis.

Assessment of the culpability ratio by Drummer provided the same result as those of Williams et al. and Terhune et al; there was a trend to a decrease in relative risk when either THC or the metabolite carboxy THC was measured in blood or urine. The relative risk was 0.6 relative to drug-free drivers, although this was not significant statistically.

7. ALCOHOL AND CANNABIS IN EPIDEMIOLOGICAL STUDIES

The relative risk for drivers with alcohol plus cannabis was also greater than that for the control group, but this culpability ratio was no different from the alcohol only group. Also in this study (as indicated above), there was no significant difference in the BAC of the alcohol-only drivers and those with alcohol plus cannabis.

The same finding was reported by Terhune who also suggested that the high levels of alcohol are primarily responsible for the increased crash risk.
Therefore the effects of alcohol in road crashes are really profound. The studies reviewed here using the method of 'responsibility analysis' have confirmed the information already established by the case-control methods-that alcohol is the dominant drug associated with risky and dangerous driving and road crashes.

There have been suggestions throughout the studies reviewed here that the crash responsibility rates associated with the low BAC plus other drug, might be higher than in the low alcohol-only groups. The interaction of other drugs and alcohol (including cannabis) require further study using epidemiological techniques. One must remember the description by Perez-Reyes of the effect of the order of administration of alcohol and cannabis in these interaction studies.

8. SUMMARY (OF THE EVIDENCE PRESENTED ABOVE)

The most recent of the reports of studies of the effects of cannabis on actual driving performance included a summary of the published literature on marijuana and driving. They concluded this review with the following paragraph:

The foremost impression one gains from reviewing the literature is that no clear relationship has ever been demonstrated between marijuana smoking and either seriously impaired driving performance or the risk of accident involvement. The epidemiological evidence, as limited as it is, shows that the combination of THC and alcohol is over-represented in injured and dead drivers and more so in those who actually caused the accidents to occur. Yet there is little if any evidence to indicate that drivers who have used marijuana alone are any more likely to cause serious accidents than drug free drivers. To a large extent, the results from driving simulator and closed-course tests corroborate the epidemiological findings by indicating that THC in single inhaled doses up to 250 µg/kg has relatively minor effects on driving performance, certainly less than BACs in the range of 0.08Ê-Ê0.10g%.

Apart from the above, a very important finding in the reviewed studies is the difference in the drug users' awareness of the effect of the drugs alcohol and cannabis. Alcohol use is accompanied by increased confidence, an impairment of judgement to the extent that driving behaviour becomes more risky, with faster speeds and a greater willingness to take risks. Cannabis use on the other hand, is accompanied by compensatory driving behaviour, including a reduced willingness to take risks and slower driving speeds. Indeed the compensation was described by Robbe and O'Hanlon in the following manner:

Very importantly our city driving study showed that drivers who drank alcohol overestimated their performance quality whereas those who smoked marijuana underestimated it. Perhaps as a consequence, the former invested no special effort for accomplishing the task whereas the latter did, and successfully. This evidence strongly suggests that alcohol encourages risky driving whereas THC encourages greater caution, at least in experiments.

The task of driving has been described as a 'self-paced' task. That is, drivers choose their own levels of task difficulty. There is a difference therefore between a driver's skills performance, as measured in individual laboratory tasks and driver behaviour. Driver performance, or skills performance is what a driver can do. Driver behaviour is what a driver actually does. Driving skills (or driver skills performance) differ very widely within a community. Some of us may be extremely cautious and others much less so. The correlation between driver skills and crash probability is not as great as many may imagine. For example, it is held by many that superior driver skills lead to reduced crashes and this led to the concept of 'advanced driver training'. Indeed, an editor of a road magazine claimed: 'I have for many years claimed that the licensed racer is far safer than ordinary chaps, on the grounds of practised skills, mental ability, cognisance of hazards in driving, keen interest in driving as well, and so on.'

In order to examine the possibility that unusually skilled drivers really did have different on-the-road driving records from the average driver, a comparison was made of the on-the-road driving records of a group of licensed racing drivers with those of other drivers matched for such characteristics as sex and age, etc. What they found was that in all measures of traffic violations including crashes, speeding violations, other moving violations as well as non-moving violations, the rates for the racing drivers exceed those of the comparison drivers, in most cases by a considerable margin.

In the light of the above, Terhune et al. asked the following questions:

A nagging question which qualifies conclusions from epidemiological studies of drugs in crashes is: If certain drugs are linked to elevated crash risks, how much of the elevation is due to characteristics of the people who use these drugs?

For example, Terhune in a literature review remarked that research revealed a striking similarity between the personal correlates of marijuana use and the correlates of crash involvement. Rebellious, deviant, youthful males were prominent among marijuana users and among those in crashes. Jessor et al. also addresses these issues.

A general conclusion made by Robbe and O'Hanlon when discussing the results of their study and of their review of the literature is worth citing here as a general conclusion to this review:

In summary, this program of research has shown that marijuana, when taken alone, produces a moderate degree of driving impairment which is related to the consumed THC dose.

The impairment manifests itself mainly in the ability to maintain a steady lateral position on the road, but its magnitude is not exceptional in comparison with changes produced by many medicinal drugs and alcohol.

Drivers under the influence of marijuana retain insight in their performance and will compensate where they can, for example, by slowing down or increasing effort. As a consequence THC's adverse effects on driving performance appear relatively small. Still we can easily imagine situations where the influence of marijuana smoking might have an exceedingly dangerous effect ie, emergency situations which put high demands on the driverÕs information processing capacity, prolonged monotonous driving, and after THC has been taken with other drugs especially alcohol.

We therefore agree with Moskowitz's conclusion that 'any situation in which safety both for self and others depends on alertness and capability of control of man-machine interaction precludes the use of marijuana'.

However, the magnitude of marijuana's relative to many other drugs' effects also justify Geringer's (1988) conclusion that 'marijuana impairment presents a real, but secondary, safety risk; and that alcohol is the leading drug-related risk factor'. Of the many psychotropic drugs, licit and illicit, that are available and used by people who subsequently drive, marijuana may well be among the least harmful.

Campaigns to discourage the use of marijuana by drivers are certainly warranted. But concentrating a campaign on marijuana alone may not be in proportion to the safety problem it causes.

~~Link to outline

[Uzi578]

The Cost of Alcohol!

By: Fritz Wiecking
Source: Washington Post
August 9, 1999

Juliet Eilperin's otherwise insightful depiction of Washington politics understated the substantive case behind the efforts of 90 organizations to include alcohol in the national youth anti-drug media campaign ["Beer Lobby Keeps Anti-Drug Drive Alcohol-Free," news story, July 23].

Health experts are nearly unanimous that alcohol is by far the leading drug of use and abuse by teenagers. It causes more deaths among teens than all other drugs combined. According to the Pacific Institute for Research and Evaluation, underage drinking costs society $58 billion per year.

Moreover, federal statistics show that drinking as a youth dramatically increases the likelihood that one will become a problem drinker or an alcoholic -- or go on to use, abuse and become addicted to other drugs. Delaying, even by a year or two, the age at which people begin to drink is one of the most effective ways to prevent drug abuse.

The public seems to understand this. In a recent national poll commissioned by Center for Science in the Public Interest, Americans reported -- by better than a 3 to 1 margin -- that the biggest drug problem faced by children is alcohol, not heroin, crack or marijuana. More than 90 percent of the respondents believed that the national anti-drug media campaign should discourage underage drinking.

FRITZ WIECKING
Manager, Federal Affairs
Center for Science in the Public Interest
Washington
© Copyright 1999 The Washington Post Company
Monday, August 9, 1999; Page A14

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[Uzi578]

No Proof Cannabis Put Drivers at Risk

Source: Advertiser, The (Australia)
October 31, 2001

Studies had found it impossible to prove cannabis adversely affected driving, an Adelaide University researcher said yesterday.

Professor Jack Maclean, director of the road accident research unit, said, while there was no doubt alcohol affected driving adversely, that was not the case with marijuana.

"It has been impossible to prove marijuana affects driving adversely," he told the Australian Driver Fatigue Conference in Sydney.

"There is no doubt marijuana affects performance but it may be it affects it in a favourable way by reducing risk-taking."

Professor Maclean said a study of blood samples taken by SA hospitals from people injured in road accidents found marijuana was the second most common drug, after alcohol, in the bloodstream.

Those with marijuana in their blood, however, were at fault in less than half of the accidents.

"Alcohol was by far the most common drug and 80 per cent of those with alcohol on board were judged to be responsible ( for accidents )," he said.

"The next most common drug, but much less, was marijuana and about 48 per cent of the people with marijuana were judged to have been responsible for their crash."

He said the lack of proof that marijuana was detrimental to driving was not because of a lack of effort by researchers.

"I can say that there are some quite distinguished researchers who are going through incredible contortions to try and prove that marijuana has to be a problem," he said.

Professor Maclean said some researchers also found the risk of crashing while driving at the speed limit in a metropolitan area actually decreased if a driver had been drinking but was under the 0.05 blood alcohol limit.

"Perhaps for some people one or two glasses of alcohol may steady them down," he said.

As speed and alcohol concentration rose, however, the risk of accidents rose exponentially. 

Newshawk: openi420
Pubdate: Wed, 31 Oct 2001
Source: Advertiser, The (Australia)
Copyright: 2001 News Limited
Contact: advedit@adv.newsltd.com.au
Website: http://www.advertiser.com.au/
Details: http://www.mapinc.org/media/1
Bookmark: http://www.mapinc.org/pot.htm (Cannabis)

~~Link to article

[Uzi578]

Australia: Cannabis Crash Risk Less: Study

Author: Penelope Debelle
Source: Age, The (Australia)
October 21, 1998

The largest study ever done linking road accidents with drugs and alcohol has found drivers with cannabis in their blood were no more at risk than those who were drug-free.

In fact, the findings by a pharmacology team from the University of Adelaide and Transport SA showed drivers who had smoked marijuana were marginally less likely to have an accident than those who were drug-free.

A study spokesman, Dr Jason White, said the difference was not great enough to be statistically significant but could be explained by anecdotal evidence that marijuana smokers were more cautious and drove more slowly because of altered time perception.

"Essentially it is the same as if there was no drug," Dr White said.

"If there is any improvement ( in driving ) I don't think it is because of the drug itself but because of what people do because the drug is there."

The study of 2500 accidents, which matched the blood alcohol levels of injured drivers with details from police reports, has policy implications for those who argue drug detection should be a new focus for road safety.

In Victoria, legislation will be introduced into Parliament in the spring session to create a new offence of driving while impaired by drugs.

Dr White said the study showed the importance of concentrating efforts on alcohol rather than other drugs.  "In Victoria particularly there is a strong move to look at cannabis and the development of roadside testing," he said.

Newshawk: kwr01@uow.edu.au (Ken Russell)
Pubdate: Wed, 21 Oct 1998
Source: Age, The (Australia)
Contact: letters@theage.fairfax.com.au
Website: http://www.theage.com.au/
Copyright: 1998 David Syme & Co Ltd
Author: Penelope Debelle

~~Link to article

[Uzi578]

Australia: Study Goes to Pot

Source: Canberra Times (Australia)
October 21, 1998

ADELAIDE: Drivers who use marijuana are less likely to cause road accidents than drunk drivers or even drug-free drivers, a study has found.

The study, the most comprehensive of its kind in the world, prompted researchers to warn against diverting resources from anti-drink driving campaigns to campaigns against driving under the influence of drugs.  Conducted by a team from the University of Adelaide's pharmacology department and Transport SA, the study used analyses of blood samples from 2500 drivers injured in accidents in South Australia.  In their attempt to define whether cannabis and other drugs played a large role in road accidents, researchers used information from the police report on each crash to determine whether the injured driver was culpable.

Drug-free drivers caused the accidents in 53.5 per cent of cases.

Injured drivers with a blood-alcohol concentration of more than 0.05 per cent were culpable in nearly 90 per cent of accidents they were involved in.  Drivers with cannabis in their blood were less likely to cause an accident, with a culpability rate of 50.6 per cent.

Newshawk: kwr01@uow.edu.au (Ken Russell)
Source: Canberra Times (Australia)
Contact: letters.editor@canberratimes.com.au
Website: http://www.canberratimes.com.au/
Pubdate: Wed, 21 Oct 1998

~~Link to article

[Uzi578]

University of Toronto Study Shows Marijuana Not a Factor in Driving Accidents

Source: ScienceDaily
March 29, 1999

The safety hazards of smoking marijuana and driving are overrated, says University of Toronto researcher Alison Smiley.

Recent research into impairment and traffic accident reports from several countries shows that marijuana taken alone in moderate amounts does not significantly increase a driver's risk of causing an accident -- unlike alcohol, says Smiley, an adjunct professor in the department of mechanical and industrial engineering. While smoking marijuana does impair driving ability, it does not share alcohol's effect on judgment. Drivers on marijuana remain aware of their impairment, prompting them to slow down and drive more cautiously to compensate, she says.

"Both substances impair performance," Smiley says. "However, the more cautious behaviour of subjects who received marijuana decreases the drug's impact on performance. Their behaviour is more appropriate to their impairment, whereas subjects who received alcohol tend to drive in a more risky manner."

Smiley, who has studied transportation safety for over 25 years, drew her results from a "metanalysis" of existing research into the effects of marijuana on driving ability, combined with traffic accident statistics in the United States and Australia. Previous studies showing stronger effects often combined "fairly hefty doses" by researchers with driving immediately after consumption, likely exaggerating the drug's effects, she believes.

While Smiley does not advocate legalizing the drug, she says her results should be considered by those debating mandatory drug tests for users of transportation equipment such as truck or train drivers, or the decriminalization of marijuana for medical use. "There's an assumption that because marijuana is illegal, it must increase the risk of an accident. We should try to just stick to the facts."

Smiley presented her findings at a symposium of the American Academy of Forensic Sciences in Florida in February. Her paper was also published in Health Effects of Cannabis, a publication of Toronto's Centre for Addiction and Mental Health, in March.

CONTACT: Bruce Rolston U of T Public Affairs (416) 978-6974 bruce.rolston@utoronto.ca

~~Link to article

[Uzi578]

Potheads Walk the Line

By: Curt Robbins
May 19, 2005

Despite studies and common sense, harsh anti-pot driving laws are becoming commonplace.

Assume that you drink two bottles of beer while watching a baseball game at home on a Saturday. Then, while driving home from work the following Thursday, you're pulled over for a broken tail light. At his own discretion, the police officer decides to test you for alcohol impairment. The beer you drank five days prior are detected. As a result, your car is impounded, you're dragged away to jail, you lose your license, and you suffer a hefty fine.

Think this sounds far-fetched? Think again. Increasingly widespread "drugged driving" laws are doing exactly this: testing for trace amounts of THC and cannabinoid metabolites that can exist in the human body for weeks, or even months, after all behavioral effects have disappeared.

"I don't know anybody who thinks it's acceptable to drive when you're impaired, whether the impairment is caused by prescription drugs, fatigue, marijuana, or anything else," Bruce Mirken, director of communications for the Marijuana Policy Project in Washington, DC, told Cannabis Culture. "But we have a huge educational job to get the public to understand that these laws literally make it a crime to drive stone cold sober."

Politicians often compare drugged driving initiatives to existing drunk driving laws, treating them as nearly identical. However, there's a basic logic to all drunk driving laws: alcohol consumption at a certain rate equals impaired driving performance, which in turn increases the chance of accidents. While the nuances of individual laws and enforcement techniques will always remain a point of contention, the basic public policy of preventing drunk driving is sound.

This is where the similarity between policies to combat drunk driving and drugged driving ends. Alcohol use has been shown to impair driving ability in hundreds of studies. However, studies into pot and driving show little or no reduction in driving ability even immediately after use.

Further, a conventional breathalyzer or even the more stringent blood alcohol analysis tests for a current level of impairment. However, drugged driving laws test not only for recent marijuana use, but also consumption that occurred weeks prior to the test. Levels of THC in the bloodstream have little to do with how high a driver might be.

Worldwide weed wars

The UK, Australia, and many states in the US currently have drugged driving laws on the books. The federal governments of Canada and the US are currently considering such laws.

Victoria, the second largest state in Australia, recently began random roadside tests for illicit drugs using a controversial saliva swab method. This imperfect technology caused significant embarrassment to the Victorian government when, during the December 1, 2004, launch, the first positive test was a well-publicized false positive for truck driver John De Jong. Subsequently cleared by independent and police lab tests, De Jong may now sue the government and Victoria police for the slur to his reputation.

The Royal Automobile Club of Victoria has voiced opposition to the roadside testing program. "The whole episode on day one and its results were a fiasco. If it continues, it will be a disaster for road safety," said public policy director Dr Ken Ogden.

In the US, new drugged driving laws are being adopted at the state level at an alarming rate. A federal measure is also being considered. If it becomes law, federal transportation funds will be withheld from states that do not comply (as has been done in the case of drunk driving laws).

Despite federal budget deficits, a poor economy, and soldiers in Iraq lacking basic flack jackets, the Bush administration's drug czar, John Walters, is spending $10 million on a single anti-drugged driving TV ad specifically aimed at teens who use marijuana.

Zero tolerance fraud

Society would consider absurd any law that criminalized drivers who consumed two ounces of beer and got behind the wheel, because, quite simply, such small amounts of alcohol don't impair driving skills. However, the most frightening variety of drugged driving policies, called zero tolerance laws, do exactly this.

Zero tolerance laws test for extremely minute quantities often any quantity of THC or cannabinoid metabolites in a driver's body. Thus, friends of medical marijuana users who are exposed to second-hand smoke, or someone who attends a rock concert or rave club, could ingest enough trace levels of THC to criminally implicate themselves.

12 US states currently have such zero-tolerance laws on the books: Arizona, Georgia, Indiana, Illinois, Iowa, Michigan, Minnesota, Nevada, Pennsylvania, Rhode Island, Utah, and Wisconsin. Each of these states criminalizes drivers who are found to have either very minute or any amount of cannabis in their bodies. Thus, a joint smoked three weeks ago for which absolutely no degradation of current driving skills exists could result in a suspended license, hefty fines, or jail time. A zero tolerance bill is also currently passing through the state legislature of Ohio.

"The prohibitionists have been very clever in choosing this as a topic to emphasize. Nobody wants impaired drivers on the road. Zero tolerance actually sounds good," explained Mirkin. "But we must explain why these laws criminalize people who are not impaired and waste resources that could do good in other ways. It's a good way to stir up fear. Prohibition depends on fear."

Med-pot and prescriptions

Another shortcoming of current drugged driving initiatives around the world is the lack of consideration for the often significantly debilitating effects of prescription drugs. A recent study revealed that 44% of Americans take prescription medication. Yet these drugged driving laws test only for illegal drugs, not prescription or over-the-counter medications.

"Some of these laws do make an exception for prescription drugs such as Marinol," said Mirken. "But it's no different than if you were smoking the natural herb. In fact, oral THC is somewhat more psychoactive. So we have this bizarre attempt to make criminals out of a particular class of citizens using a natural substance because they are socially disfavored and a good whipping boy for politicians."

Canada and 10 states in the US permit licensed use of medical marijuana by their citizens. Sponsors of drugged driving bills don't seem to consider that sufferers of chronic pain, wasting syndromes, and spasticity disorders actually increase their driving skills after consuming moderate doses of cannabis to alleviate their debilitating symptoms. Policy makers also do not consider that many pharmaceutical drugs cause side effects that are markedly more detrimental and dangerous than a standard dose of cannabis.

Sadly, these drugged driving laws have little to do with traffic safety; their true purpose is to persecute pot smokers for their lifestyle choice. If left unchecked, this trend could result in total prohibition from the roads, with regular drug tests required to get and keep any sort of driver's license.

~~Link to article--top article

[Uzi578]

Stoned Drivers are Safe Drivers

By: Curt Robbins and Dana Larsen
January 11, 2005

Two decades of research show that marijuana use may actually reduce driver accidents.

The effects of marijuana use on driving performance have been extensively researched over the last 20 years. All major studies show that marijuana consumption has little or no effect on driving ability, and may actually reduce accidents. Here's a summary of the biggest studies into pot use and driving.

A 1983 study by the US National Highway Transportation Safety Administration (NHTSA) concluded that the only significant affect of cannabis use was slower driving - arguably a positive effect of driving high.

A comprehensive 1992 NHTSA study revealed that pot is rarely involved in driving accidents, except when combined with alcohol. The study concluded that "the THC-only drivers had an [accident] responsibility rate below that of the drug free drivers." This study was buried for six years and not released until 1998.

A 1993 NHTSA study dosed Dutch drivers with THC and tested them on real Dutch roads. It concluded that THC caused no impairment except for a slight deficiency in the driver's ability to "maintain a steady lateral position on the road." This means that the THC-dosed drivers had a little trouble staying smack in the center of their lanes, but showed no other problems. The study noted that the effects of even high doses of THC were far less than that of alcohol or many prescription drugs. The study concluded that "THC's adverse effects on driving performance appear relatively small."

A massive 1998 study by the University of Adelaide and Transport South Australia examined blood samples from drivers involved in 2,500 accidents. It found that drivers with only cannabis in their systems were slightly less likely to cause accidents than those without. Drivers with both marijuana and alcohol did have a high accident responsibility rate. The report concluded, "there was no indication that marijuana by itself was a cause of fatal accidents."

In Canada, a 1999 University of Toronto meta-analysis of studies into pot and driving showed that drivers who consumed a moderate amount of pot typically refrained from passing cars and drove at a more consistent speed. The analysis also confirmed that marijuana taken alone does not increase a driver's risk of causing an accident.

A major study done by the UK Transport Research Laboratory in 2000 found that drivers under the influence of cannabis were more cautious and less likely to drive dangerously. The study examined the effects of marijuana use on drivers through four weeks of tests on driving simulators. The study was commissioned specifically to show that marijuana was impairing, and the british government was embarrassed with the study's conclusion that "marijuana users drive more safely under the influence of cannabis."

According to the Cannabis and Driving report, a comprehensive literature review published in 2000 by the UK Department of Transportation, "the majority of evidence suggests that cannabis use may result in a lower risk of [accident] culpability."

The Canadian Senate issued a major report into all aspects of marijuana in 2002. Their chapter on Driving under the influence of cannabis concludes that "Cannabis alone, particularly in low doses, has little effect on the skills involved in automobile driving."

The most recent study into drugs and driving was published in the July 2004 Journal of Accident Analysis and Prevention. Researchers at the Dutch Institute for Road Safety Research analyzed blood tests from those in traffic accidents, and found that even people with blood alcohol between 0.5% and 0.8% (below the legal limit) had a five-fold increase in the risk of serious accident. Drivers above the legal alcohol limit were 15 times more likely to have a collision. Drugs like Valium and Rohypnol produced results similar to alcohol, while cocaine and opiates showed only a small but "not statistically significant" increase in accident risk. As for the marijuana-only users? They showed absolutely no increased risk of accidents at all.

LINKS AND REFERENCES

1983 National Highway Transportation Safety Administration study: Stein, AC et al., A Simulator Study of the Combined Effects of Alcohol and Marijuana on Driving Behavior-Phase II, Washington DC: Department of Transportation (1983)
www.erowid.org/plants/cannabis/cannabis_myth12.shtml

1992 National Highway Transportation Safety Administration study: The Incidence and Role of Drugs in Fatally Injured Drivers, by K.W. Terhune, et al. of the Calspan Corp. Accident Research Group in Buffalo, NY (Report # DOT-HS-808-065)
www.drugsense.org/tfy/nhtsa1.htm

1993 National Highway Transportation Safety Administration study: Marijuana and actual Driving Performance, By Hindrik WJ Robbe and James F O'Hanlon. Institute for Human Psychopharmacology, University of Limburg
www.erowid.org/plants/cannabis/cannabis_driving4.shtml

1998 University of Adelaide and Transport South Australia study:
www.ukcia.org/research/driving4.html

1999 University of Toronto Study, Marijuana Not a Factor in Driving Accidents:
newsandevents.utoronto.ca/bin/19990329a.asp

2000 UK Transport Research Laboratory study on Cannabis and Driving:
www.mapinc.org/newscc/v00/n1161/a02.html

2000 UK Department of Transportation's Cannabis and Driving report:
www.dft.gov.uk/stellent/groups/dft_rdsafety/documents/page/dft_rdsafety_504567.hcsp

2002 Report of the Special Senate Committee on Illegal Drugs
www.parl.gc.ca/37/1/parlbus/commbus/senate/com-e/ille-e/rep-e/repfinalvol1part4-e.htm

July 2004, Journal of Accident Analysis and Prevention, Psychoactive substance use and the risk of motor vehicle accidents.
www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15094417

For a less scientific and more amusing study of the combination of drugs and driving, go here:
www.techno.de/mixmag/interviews/Driving_on_drugs.html

~~Link to article

[Uzi578]

A Better Way to Test

By: Dana Larsen
January 11, 2005

Performance testing provides a valid alternative to zero tolerance drugged driving tests.

A better way of keeping impaired drivers off the road, or out of a safety-sensitive workplace, is to use performance testing.

A performance test doesn't measure what is in your bloodstream, it measures your hand-eye coordination, reaction time, and other indicators of your current driving ability.

Drug tests can only pick up on substances they test for, so someone impaired on an unusual drug, or a prescription, will typically escape detection. Also, a performance test will detect any kind of impairment, including that which doesn't relate to substance use, such as fatigue, hangover or emotional upset.

Roadside performance testing is already common. When a police officer asks a driver to walk a straight line, touch his nose or count backwards, the driver is being tested for his ability to perform, regardless of what may be in his bloodstream. However, this kind of testing is subjective and not standardized.

One standardized performance test gaining popularity in the workplace is a computer-based "critical tracking test." This test has the user operate a knob to try to keep a randomly veering cursor centered on a video screen. This kind of testing is cheaper, faster and more accurate than urine testing for determining current impairment. This kind of simple test could easily be adapted for roadside use, and given by police to drivers suspected of any sort of impairment.

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[Uzi578]

Stoned Drivers are Safe Drivers

*Not the same as the article above

By: Dana Larsen
December 26, 2000

UK cops are testing for "drugged drivers" despite studies which show stoners drive safely.

UK cops are persisting in introducing a series of roadside tests for stoned drivers, despite a study released by the UK Transport Research Laboratory in August 2000, which found that pot-smoking has a minimal if not beneficial effect on driving performance.

The government-funded study was launched under pressure from anti-drug and driving groups, and was an embarassment to the British Ministers who had expected it to support their anti-stoned-driving campaigns.

The British study confirmed the results of a wide variety of research into stoned driving from around the world:

A 1983 study by the US National Highway Transportation Safety Administration (NHTSA) used stoned drivers on simulators, and concluded that the only statistically significant effect associated with marijuana use was slower driving.

A comprehensive 1992 study by the NHTSA found that marijuana is rarely involved in driving accidents, except when combined with alcohol. It concluded that "the THC-only drivers had an [accident] responsibility rate below that of the drug free driversS While the difference was not statistically significant, there was no indication that cannabis by itself was a cause of fatal crashes." This study was buried for six years and not released until 1998.

Another NHTSA study performed in 1993 dosed Dutch drivers with THC and tested them on real Dutch roads. It concluded that "THC's adverse effects on driving performance appear relatively small."

A massive 1998 study by the University of Adelaide and Transport South Australia analyzed blood samples from 2,500 accidents, and found that drivers with cannabis in their system were actually slightly less likely to cause accidents than those without.

A University of Toronto study released in March 1999 found that moderate pot users typically refrained from passing cars and drove at a more consistent speed than non-users.

An important consideration when considering the effects of cannabis and driving is whether the smoker is an experienced user. Novice tokers typically experience more difficulty driving than regular users.

The British study also found that tiredness caused 10% of all fatal accidents, compared with 6% for alcohol.

Roadside testing

Despite these many conclusive results, UK cops are promoting their new roadside tests for "drugged drivers."

Drivers being tested for stonedness must estimate the passage of 30 seconds, walk a straight line while watching their feet, have their pupils examined for dilation or constriction, and finally be forced to stand on one leg with their head tilted back, eyes shut, arms extended, and touch their nose three times with each hand. (This last one is not easy even for the very sober - try it.) Perhaps most importantly, officers are instructed to pay attention for "herb-like smells" during the tests.

Those who fail any aspect of the test must provide a blood sample for drug testing. Failing or refusing the blood sample brings a conviction for "drugged driving."

British police bragged they would be able to test 20,000 drivers each year, leading to a 10-fold increase in arrests and charges.

~~Link to article

[Uzi578]

Driving High

By: Reverend Damuzi
December 9, 2002

Ontario lawyer driving high, organizing rallies and fighting corruption.

Former lawyer Rick Reimer was charged with driving under the influence after he was pulled over while smoking a joint on February 11, 2002. Rather than put it out, he calmly continued toking as the cop approached his vehicle and asked for his license.

"Is that cannabis?" the bewildered cop asked, his jaw dropping at Reimer's brazen puffing. The last person he pulled over might have been a farmer chewing a stalk of wheat on a tractor.

"Eventually it came down to him saying, 'you can't smoke and drive; you're impaired,'" recounted Reimer. "He claimed I was weaving over the centre line, which was pure bogus, but it was an excuse to have a dispute with me. He saw my behavior as being a confrontation with him, and in a sense it was, but it is an issue that in my opinion has to be litigated."

Reimer hopes the local courts will put truth above small-town politics. Nestled on the hip of Ontario's rugged Algonquin park, Reimer's home of Barry's Bay is one of those rural pockets, originally settled by conservative religious folk, that stuffed itself full of hippies during the Vietnam war, producing unusual lifestyle contrasts, a strange blend of pot tolerance and intolerance, running through the community like hot and cold currents in a river. In Barry's Bay, Rick Reimer is like molten lava bubbling to the surface, a reflection of Reimer's repulsion to submerging his personal truths under the slick, still waters of legal professionalism.

"Here I was defending people and thinking, 'there, but the for the grace of God, go I.' Especially having a judge look me straight in the eye and say, 'your client is scum because he smokes marijuana,' and then hearing him say right afterwards, 'you are probably one of the best lawyers that appears in front of me.' I thought I had to do something to end that hypocrisy. It was about six months afterwards [in 1998] that I came out publicly, and about another six months afterwards that I was diagnosed with MS [Multiple Sclerosis], which gave me a legitimate medical reason to smoke."

Since "coming out", Reimer was one of the first to receive a medical marijuana exemption from the Canadian Government in 2000, and was instrumental in organizing major political pot protests in his home province of Ontario, including the 2002 Million Marijuana March in Ottawa. He also hosts a radio show in Killalloe, and once smoked a vaporizer full of dank buds with Federal Marijuana Party Leader Marc Boris St Maurice before a room full of Canadian Senators. It happened during his presentation to the Senate's Special Committee on Illegal Drugs when it met last May to reconsider Canada's drug laws.

"Boris wanted to smoke it with tobacco," said Reimer. "But one of the senators demurred, and said Mr Reimer probably needs some marijuana put some marijuana in there!"

Activist ally

One friend of Reimer's, Rob Brown, told me how Reimer helped Brown get his exemption, so that he could use cannabis to treat a life-threatening combination of Hepatitis and multiple cancerous tumors on his liver, spleen, prostate and bladder, without fear of police harassment. In January 2000, Reimer encouraged Brown to camp out on the steps of Ottawa's Parliament Hill.

"I had decided that I would camp there and puke and shit until they gave me my exemption," said Brown. "I was fed up enough that I would have stayed there until they either gave me my exemption or I died."

Near death, but still clinging to the rough steps of our nation's halls of power during an icy Canadian winter, it took Brown two days to embarrass Health Canada into forking over the exemption he had been waiting a year to receive. Sadly, despite his exemption, Brown was raided on July 25, 2002. As he had a few more green sisters than his med-pot permit allowed, police seized about 150 of them, but showed some compassion when they left Brown with 350 others for medicine.

Brown also told me how Reimer provided the money Brown needed to buy some land and a home; how Reimer had done more for him than many people do for their own family.

Although Reimer's illness forced him to retire from law in 2000, he had already spent countless hours on pro-bono cases for people throughout the community, some of whom I had an opportunity to meet personally. Reimer also once defended a 14-year-old boy busted for cannabis at school.

"It was perhaps enough to get a dozen of his friends high," said Reimer. "I was fighting to keep him out of jail, but the judge gave him three days, as a sort of compromise. If he had forced himself sexually on a 10 year old, or if he had brought a 40 oz bottle of alcohol into the school, they would have tried to find some way around putting him in jail but because it was cannabis, they put him away."

While in Barry's Bay, three people told me that Ontario Provincial Police bullies detested Reimer, and were looking for some way to get at him.

"I can speculate on the reasons," said Reimer. "I've been told by many people that when they were being busted and shaken down cops asked them, 'what do you know about Reimer, tell us something and things will go better for you.' Why it's happening? I think police are by and large cowards. They are afraid to look freedom in the eye, so they are looking at ways to strike at me and so to strike at the cause that I stand for. But they won't come up to me and say anything to my face. They would rather do it behind my back, paying off some informer with money or mercy."

Driving high

Reimer was enjoying the legal protection of his exemption when he was pulled over that fateful day last February. The cop couldn't charge Reimer with possession, and couldn't take away his cannabis. Yet here was Reimer pot-advocate Reimer, legally-suave Reimer, much-despised by police Reimer openly blazing a stick of weed right in the cop's face.

Reimer had researched the science. Holland's Institute for Human Psychopharmacology concluded that marijuana has a relatively small effect on driving performance. A US National Highway Transporation Safety Administration study found that marijuana is rarely involved in traffic accidents unless mixed with booze. Australia's University of Adelaide that found stoned drivers were less likely to cause accidents (CC#29, Stoned drivers are safe drivers).

"I know that smoking does not impair my ability to drive one bit," he asserted. "It enhances my ability to drive. But I still have to be prepared to deal with people who have the mentality that cannabis is just some different kind of alcohol. There are some people that still believe that. The crown attorney's office is calling an expert witness who is going to say that marijuana is worse than alcohol, that any consumption of any amount of marijuana by any person must impair that person's ability to drive."

"I will argue that not everyone is impaired by the consumption of marijuana. Everyone has different tolerance levels. If I can argue that successfully, then it is simply a matter of 'am I one of those people?' It would help if people could send letters saying 'I smoke and drive' and that not everyone is impaired by the consumption of marijuana. They can even write anonymously. It will help."

The date of Reimer's trial is December, 12, 2002. Letters can be sent to his address, below.

Rick Reimer: RR2, Barry's Bay, Ontario, Canada, K0J 1B0
For more on cannabis and driving: www.cannabisculture.com/news/driving

~~Link to article