Wildlife officials say they are trying to figure out how to cope with a growing problem in the state: black bears wandering into roadways and being struck by vehicles. Game warden Sean Fowler said the crashes are becoming more common. Last week, Fowler responded to one such accident on Route 2 in Marshfield; the 120-pound male bear died and the vehicle that hit it had left the scene by the time the officer arrived. ‘‘It’s going to happen with more regularity because the bear population is higher than it’s ever been,’’ Fowler said. Mark Scott, director of wildlife for the Vermont Fish & Wildlife Department, said the state’s black bear population has roughly doubled since the 1980s, to more than 6,000 today. From 2005 to 2007, an average of 42 bears a year were struck and killed by vehicles; from 2010 to 2012, the average was 60 each year, according to the department’s law enforcement division.