Yes, that cannabis is not a big problem when it comes to driving. It's not true. All the evidence suggests that it does increase crash risk, approximately doubles crash risk in cannabis users. It's far worse if you use it together with alcohol. I guess some of that perception may be in comparison with alcohol, where we know that the crash risk goes up exponentially at higher alcohol levels. Cannabis is not as bad as alcohol in terms of causing an increased crash risk, but it certainly does cause an increased crash risk.
On September 18th, 2017. See this statement in context.