Matt Kelley blogs on criminal justice issues at change.org, and I rarely agree with him. But like the proverbial stopped clock:

Advocates for marijuana reform frequently argue that the drug should be legalized because it's safe.... But when it comes to driving and safety, legalization advocates often go a step too far -- claiming that driving under the influence of marijuana is not dangerous and that marijuana causes zero deaths each year.  These misleading arguments are harming the reform movement.

It's a fact: marijuana impairs driving ability. Reliable scientific studies have shown that marijuana usage causes slower reaction time, impairs eye tracking and lateral awareness and that drivers fail to reliably regulate speed and the distance between their car and the car ahead of them. Driving ability is especially bad when the a person has smoked recently.