Actually, it's not a simple matter. Studies in the US, where recreational cannabis use has been legalised on some states, are inconclusive when it comes to marijuana-related traffic accidents. Broadly, they tend to show an increase immediately after legalisation which then returned to normal.

That said, any increase in traffic accidents is always unwelcome and the question must be asked - will legalising marijuana put innocent people at greater risk on our roads?

Plenty of studies indicate THC, the psychoactive ingredient that makes pot smokers high, impairs drivers' ability to stay focused and judge speed and distance. What is unclear, however, is the level of impairment caused by smoking a joint several hours, a day or a week before getting behind the week. Roadside drug tests can detect the presence of THC in the bloodstream but not the level of impairment of the driver's ability to drive safely.

Unlike the blood alcohol level, which can be measured and matched to an impairment level - over 0.05 and you can't drive - the presence of THC is not a measure of impairment. There has been considerable contention as roadside drug testing has been rolled out because someone who puffed on a joint several days ago can face the same charges as someone who lit up just before setting out on their journey.

So while legalising pot use might address some of the social issues caused by criminalising what is essentially a health issue, as the drug law reform lobby consistently argues, it has the potential to have unforeseen consequences as well.

We know smoking anything is bad for health and cannabis is no different. Will sanctioning its use lead to an increase in respiratory illnesses? We know cannabis impairs drivers so will legalising its use add another peril to our already dangerous roads?

Is all this risk worth it if it means harm is reduced in other ways by keeping people out of the justice system? The ACT experiment may provide answers down the track.