The Maine Turnpike is opening its first high-speed toll plaza. Beginning Monday, drivers who use E-ZPass can pay their tolls electronically while driving at highway speeds at the plaza in New Gloucester. The Maine Turnpike Authority says there’s one high-speed lane in each direction and three other lanes that can be used by cash or E-ZPass drivers traveling at slow speeds. The system works with overhead equipment detecting a vehicle’s E-ZPass tag and automatically deducting the correct amount from the driver’s account. Turnpike officials say the system will add convenience for motorists, cut operating costs and reduce vehicle emissions. About 80 percent of the turnpike’s commercial traffic and 60 percent of passenger vehicles pay tolls electronically.