What does marijuana legalization mean for stoned driving?

Cannabis is becoming more popular across the US. Four states have legalized recreational marijuana and five more, including California, will vote on the issue next Tuesday. This is good news for many, but there is one big downside: legal pot can be a public safety nightmare.Several studies have shown that stoned driving can be dangerous. But how can law enforcement test if a driver is stoned and impaired? Traditional blood tests that might work for alcohol don’t work for marijuana. This cr