Marijuana makes driving safer

SUBHEAD: Study says medical marijuana use reduces traffic deaths acting as alcohol substitute.  

By Staff on 30 November 2011 for Huffington Post - 

Image above: Driving under the influence of marijuana. From article below.
A good deal of time, money, and energy has been spent on the issue of drinking and driving. For all the hype surrounding medical marijuana these days, however, not only is anti-driving advocacy weak -- data on the effects of marijuana and traffic deaths is sparse as well. CU Denver economics professor Daniel Rees and Montana State University assistant economics professor D. Mark Anderson hope to change that.

In a recently released study, the duo analyzed state-level data for correlations between medical marijuana laws and a variety of outcomes. An abstract details some of their more surprising findings:
Legalization of medical marijuana is associated with increased use of marijuana among adults, but not among minors. In addition, legalization is associated with a nearly 9 percent decrease in traffic fatalities, most likely to due to its impact on alcohol consumption. Our estimates provide strong evidence that marijuana and alcohol are substitutes.
The authors accounted for variables including seat-belt usage, miles driven, and changes in traffic laws, though don't explicitly draw a 1-to-1 correlation between marijuana usage and decreased traffic fatalities. They further acknowledge "cannabis use impairs driving-related functions such as distance perception, reaction time, and hand-eye coordination," though drivers "under the influence of marijuana reduce their velocity, avoid risky maneuvers, and increase their 'following distances.'"

The report concludes that marijuana legalization is associated with a 12-percent drop in alcohol-related fatal crashes, and a 19-percent decrease in the fatality rate for people in their 20s. Despite the decrease in both rates, the study emphasizes it is not necessarily safer to drive under the influence of marijuana than alcohol -- just that medical-marijuana usage alters the likelihood of driving.
Read study here (

Marijuana May Not Impair Driving  

Does marijuana really affect your ability to drive safely? An Orange County, California attorney says there's evidence to show it doesn't -- and testing for the presence of marijuana doesn't measure impairment, anyway.

Drunk driving laws today typically define "driving under the influence" as covering both alcohol and drugs, with marijuana included as "drugs." In most states, the very presence of marijuana in a driver's blood is either illegal in itself, or is considered proof of impairment.

"The prevailing view for years has been that cannabis, like alcohol, impairs the coordination, reflexes, perception and judgment necessary for the safe operation of a vehicle," said DUI attorney Lawrence Taylor.
But none of us has the pot equivalent of those ubiquitous "I was so drunk I totaled my car when I was a teenager" type of stories. And the highway carnage that would accompany marijuana's popularity -- like that which has accompanied alcohol's -- seems never to have happened.
The blood or urine tests typically used to determine the presence of marijuana metabolites don't measure impairment or intoxication; in fact, such tests can detect marijuana days or even weeks after it was last ingested, long after any "impairment" is in the distant past.
The federal government's Department of Transportation (DOT) did research with a fully interactive simulator on the effects of alcohol and marijuana, alone and in combination, on driver behavior and performance ("The Effects of Alcohol on Driver-Controlled Behavior in a Driving Simulator, Phase I," DOT-HS-806-414). The study found that alcohol consistently and significantly caused impairment -- but that marijuana only had an occasional effect.
Further, contrary to drug warrior mythology, there was little evidence of interaction between alcohol and marijuana.
Speeding tickets and accidents went up with the use of alcohol, but no marijuana influence on speeding and accidents was noted. Additionally, alcohol-impaired drivers who also smoked marijuana showed no additional impairment from the pot.
The California Department of Justice came to a different conclusion, claiming that marijuana does impair driving skills, particularly at high-dose levels or among inexperienced users ("Marijuana and Alcohol: A Driver Performance Study," California Office of Traffic Safety Project No. 087902).
But a more recent federal study found that "THC [the active ingredient in marijuana] is not a profoundly impairing drug... It apparently affects controlled information processing in a variety of laboratory tests, but not to the extent which is beyond the individual's ability to control when he is motivated and permitted to do so in driving" ("Marijuana and Actual Performance," DOT-HS-808-078).
The federal study says that "It appears not possible to conclude anything about a driver's impairment on the basis of his/her plasma concentrations of THC... determined in a single sample."
"In other words, (1) marijuana may not impair driving ability at all, and (2) the blood 'evidence' usually measures only an inactive substance which may have been present for days," said Taylor.
"Prosecutors readily acknowledge that a person who smoked a week earlier couldn't possibly be impaired by marijuana, and yet they still prosecute, and often win, these cases," noted a commenter on Taylor's webpage.


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