As more and more states allow medical marijuana and some states, Colorado and Washington have a form of legalized marijuana, the law is going to need to grapple with how cannabis use can affect driving. Washington state set a limit of 5 nanograms of THC for every milliliter of blood.

CNN decided to find out how much this would affect drivers.  Their affiliate, KIRO, asked drivers to smoke marijuana and drive.  The results were surprising.

The drivers performed relatively well even at amounts well above Washington’s legal limit. Some smokers have protested that they drive better while under the influence of cannabis. There seems to be no evidence for that but neither is there evidence that pot smokers perform nearly as poorly as alcohol drinkers. A previous 2010 double blind study with 85 participants appeared to show that smoking a joint containing 2.9% THC doesn’t affect driving ability. (Though those receiving cannabis did reduce their speed.)

LoCO, however, does not advocate driving while using any intoxicating substance.