This can be difficult to prove in many instances, however, because marijuana has a relatively short high. It can also stay in a user’s system for up to 30 days, which means that a person may test positive for marijuana even if he or she did not smoke it prior to or while driving a vehicle.
Many assume that like alcohol, cannabis impairs the coordination, perception, sense of judgment, and reflexes needed to operate a vehicle safely. Findings from various studies though, including some from the U.S. National Highway Transportation Safety Administration, do not always support this opinion.
According to these studies, drunken drivers drive differently from those high on marijuana. Motorists under the influence of marijuana have a tendency to drive slower and have accident responsibility rates that are lower than those of drug free drivers. Drunken drivers operate their vehicles faster than normal and are known to overestimate their skills, while the opposite is true for drivers impaired with marijuana. The shortfalls in driving stoned only become more apparent when the driver faces an unexpected situation or is handling multiple tasks at once.
Research on alcohol and marijuana effects were conducted using a fully interactive simulator, and results showed that marijuana only had an occasional effect on an individual’s impairment, while alcohol consistently and significantly caused impairment. Studies also showed that alcohol intake increased the number of accidents and speeding tickets issued, but no such results were noted for marijuana use or combined use of alcohol and marijuana.
Due to the complex and varying effects of drugged driving, many states have difficulty developing and implementing DUI laws on marijuana that are fair and effective. This is why researchers continue to find a solid connection between marijuana DWI and elevated accident risk.
Source: 2013 Minnesota Statutes, published