He Marijuana Impair Driving?

It 's against the law to drive under the influence of marijuana. It has always been assumed that cannabis, like alcohol, impairs the perception, coordination, reflexes and judgment necessary for safe operation of a motor vehicle. And, of course, there have been studies addressed the question of government: marijuana impair driving?

Interestingly, however, the results do not necessarily support popular opinion ....

On the one hand, the California Department of Justice has found that marijuana impairs psychomotor performance without a doubt that they are functionally related to driving and that driving skills may be impaired, particularly at high dose levels or among inexperienced users. "Marijuana and alcohol: a study of driver performance," California Office of Traffic Safety Project No. 087902 (September 1986).

In contradiction with these conclusions, however, are two federal studies. The U.S. Department of Transportation has conducted research with a fully interactive simulator on the effects of alcohol and marijuana, alone or in combination, on driver-controlled behavior and performance. Although alcohol was found consistently and significantly to cause impairment, marijuana had only an occasional effect. In addition, there was little evidence of interaction between alcohol and marijuana. Accidents and reliable for speeding is increased with alcohol, but no marijuana or combined alcohol-marijuana influence was observed. "The effects of alcohol on behavior controlled by the driver in a driving simulator, Phase I", DOT-HS-806-414.

A more recent report entitled "Marijuana and its Performance", DOT-HS-808-078, noted that "THC is not a profoundly impairing drug .... It apparently affects controlled information processing in a variety of laboratory tests, but not the level that is beyond the individual's ability to control when it is motivated and permitted to do so in the guide. "

The study concluded that: "... An important practical objective of this study was to determine if the degrees of impaired driving can be effectively provided by a measured concentration of THC in plasma or performance measured in potential along the road" sobriety "evidence of ability or hand and monitoring the stability of posture. The results, like many reported before, indicated that none of these measures provides precise changes in actual performance under the influence of THC ...".

The researchers found that "it appears possible to conclude anything about the driver's impairment on the basis of its plasma concentrations of THC and THC-COOH determined in a single sample." Note: "THC" stands for Delta-9-tetrahydrocannabinol, which is the intoxicating ingredient in marijuana. THC is fairly quickly converted by the body into inert metabolites, which may remain in the body for hours or even days. It is these metabolites that police blood tests in DUI arrests detect and measure.

In other words, (1) marijuana may not impair driving ability at all, and (2) "evidence" of the blood measures only an inactive substance which may have been there for days....