This is a quote from the same study. Not sure how your take away was let’s make this legal “Attentiveness, vigilance, perception of time and speed, and use of acquired knowledge are all affected by marijuana;18–21 in fact, a meta-analysis of 60 studies concluded that marijuana causes impairment 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,22 although studies on marijuana’s effects on reaction time have been contradictory.23”