AUGUSTA — State and federal public safety officials unveiled a vehicle Wednesday that’s designed to make roadside testing of drivers suspected of impaired driving safer, faster and easier for law enforcement agencies. The 37-foot truck, bought using a nearly $300,000 grant from the National Highway Traffic Safety Administration, is going to give “all police departments and law enforcement a great opportunity to help defeat impaired driving,” Department of Public Safety Commissioner John Morris said at a news conference at the Maine Bureau of Highway Safety. “There’s a lot of people dying because drivers are impaired,” Morris said.