Marijuana use has not been found to increase the risk of car crashes, according to a new federal report. Studying car accidents in Virginia Beach, Va., during a 20-month period ending in 2012, researchers randomly sampled 3,000 accident-involved drivers and found no evidence suggesting those with marijuana in their system were more prone to accidents, according to a National Highway Traffic Safety Administration report released Friday. When researchers controlled for factors such as age and gender, they found no evidence marijuana use increases accident risks. This was despite the fact that, in the study, drivers who tested positive for marijuana...