PBS News Weekend

Massachusetts is on the verge of becoming the seventh state in the country with legal recreational marijuana dispensaries. But while regulators and the marijuana industry there prepare to become the first legal retail weed on the East Coast, public safety advocates and law enforcement are concerned there will be more drivers operating vehicles on the road while they are high. As the national trend towards marijuana legalization continues, states are exploring new ways to measure how to definitively tell when a driver who smoked marijuana is too high to be on the road. NewsHour Weekend's Hari Sreenivasan reports.