The fact that South Africans may now legally grow dagga in their gardens will undoubtedly lead to an increase in cannabis consumption. The effect that this will have on road safety still has to be determined.
In America, though, two new studies show that in the states where recreational marijuana is legal there was no increase in crash-related fatalities compared to other states.
Insurance claims data show that Colorado, Washington and Oregon all experienced an increase in auto accident claims after retail marijuana sales became legal, according to research by the Highway Loss Data Institute (HLDI).
But Washington and Colorado had similar rates of traffic fatalities as eight other states that haven't legalised recreational pot, an analysis of federal crash data published in the American Journal of Public Health found.
The conclusions of the two separate studies don't necessarily conflict, said J.T. Griffin, chief government affairs officer for Mothers Against Drunk Driving, a nonprofit organisation in the United States and Canada that attempts to stop driving under the influence of alcohol or any other drug.
"One of the characteristics of a driver who's on marijuana is they tend to drive more slowly," Griffin said. "If they're doing that but they're impaired, to me that would imply to me there would be more fender-benders. There would be more rear-end collisions and people running off the road and those kinds of things."
Concern not misplaced
Analysis of insurance claims revealed that states experienced a combined an increase of 2.7% in collision claims when recreational marijuana hit the open market, compared to other nearby states, according to the HDLI.
Increases in collision claims varied by state:
- Colorado experienced a 14% increase in collision claims compared with nearby Nebraska, Utah and Wyoming.
- Washington underwent a 6% increase compared to Idaho and Montana.
- Oregon had a 4% increase compared to Idaho, Montana and Nevada.
"Worry that legalised marijuana is increasing crash rates isn't misplaced," David Zuby, executive vice president and chief research officer for the Insurance Institute for Highway Safety, said in a statement. "HLDI's findings on the early experience of Colorado, Oregon and Washington should give other states eyeing legalisation pause."
However, a separate review of traffic fatality data kept by the Federal Highway Administration showed that fatal wrecks occurred in Washington and Colorado at about the same rate both prior to and following implementation of legal marijuana.
Year-over-year changes in crash fatality rates in the two recreational pot states were similar to those in Alabama, Indiana, Kentucky, Missouri, South Carolina, Tennessee, Texas and Wisconsin, said lead researcher Dr Jayson Aydelotte. He's a trauma surgeon with Seton-Dell Medical Center at the University of Texas-Austin.
More drugged drivers
Recreational marijuana laws have amounted to a "giant social experiment", Aydelotte said, and officials are now finding out how legal pot can affect public safety.
So far, eight states and the District of Columbia have passed laws legalising recreational pot sales, according to NORML, a group advocating for the reform of marijuana laws.
"One of the claims was that if you legalise marijuana, you're going to have a whole population of drugged drivers out there and have more traffic deaths," Aydelotte said. "It looks like there's no statistically significant difference before or after, or compared to control states that didn't have those laws passed."
Findings from the crash fatality study "ought to be reassuring to lawmakers and those in the public who possessed concerns that regulating adult marijuana use may inadvertently jeopardise public safety," said Paul Armentano, deputy director of NORML.
But Dr Scott Krakower, assistant unit chief of psychiatry at Zucker Hillside Hospital in Glen Oaks, New York, noted concerns that pot can increase the overall risk of vehicle accidents.
In South Africa the Road Traffic Management Corporation (RTMC) annual road death statistics "are cause for great concern", and we definitely don't need anything to worsen the situation.
A lot more to learn
"The public should therefore interpret this study with caution until further research is conducted," Krakower said of the traffic fatality study.
Griffin said the two studies show that more needs to be done to understand the potential effects of marijuana on driving ability.
"We certainly know it's never good to use an impairing substance and then drive, but marijuana affects the body very differently than other drugs do," Griffin said. "We have a lot more to learn. It is something states need to look at when they're considering legalisation."
One particular challenge is coming up with a way to judge whether driving ability has been impaired by pot. Marijuana does not lend itself to something as simple as a blood alcohol test, Griffin said, which means law enforcement will need even more training to be able to enforce impaired driving laws against drivers under the influence of pot.
"Frankly, there may never be a .08 standard because of the way the drug works," Griffin said, referring to the standard blood alcohol level for drunk driving.