As a recent review of the evidence
by R. Andrew Sewell
, James Poling
and Mehmet Sofuoglu
(all of Yale University’s School of Medicine) demonstrates, the debate about cannabis use and dangerous driving is more complex than one might think.
Studies show that “attentiveness, vigilance, perception of time and speed, and use of acquired knowledge” are all impaired by marijuana. In fact, an analysis of 60 studies performed by G. Berghaus and B. Guo found that marijuana impairs you “in every performance area that can reasonably be connected with safe driving of a vehicle, such as tracking, motor coordination, visual functions, and particularly complex tasks that require divided attention.”
On the other hand, some lab experiments show that drivers who are intoxicated with marijuana perform little worse than sober ones
, except when the marijuana is combined with alcohol. Many researchers have concluded that this is because drivers who are high are very aware that they are impaired, and deal with their neurological and psychological deficiencies by adopting coping mechanisms to compensate, even over
compensate, for their altered state. This arguably leads to stoned drivers driving at lower speeds, leaving greater following distances between cars and making fewer efforts to pass other vehicles.
Interestingly, it seems that marijuana impairs “automatic” functions, like reaction time or the ability to stay in one’s lane, while leaving “cognitive” functions, for example, the choice of speed, comparatively intact. Alcohol, on the other hand, degrades cognitive function, with drunks much more prone to making risky choices behind the wheel.
Lab experiments may be a poor reflection of real-life driving behavior: after all, subjects know they’re being studied. Lab work is a better reflection of what people can do than what they actually do.
If you are driving high, beware. Michigan drivers could become the first in the nation subject to roadside drug testing
under a bill introduced to the Legislature just a few months a go. The legislation would authorize police to administer a roadside saliva test for illegal drug use, just as they do breath tests for alcohol, when they stop a driver suspected of being intoxicated. The test kit under consideration for Michigan can detect drug use in six categories, including marijuana, cocaine and methamphetamine.
What do you think about driving high?
Is it more dangerous than driving drunk or buzzed off of alcohol?