Pilot project lets drivers buy gas with a smartphone and an E-ZPass

An overhead scanner identifies a car as it pulls into the gas station. Just as the driver hits the brakes, his phone buzzes with a question: “PayByCar today? Reply with pump number to activate.”

The driver presses “5,” and by the time he steps out of the car, his credit card has been authorized. The gas is ready to pump.

The futuristic new payment option at the Alltown Mobil station on Route 9 takes advantage of a device that millions of drivers already have in their vehicles: an E-ZPass toll transponder. On Monday, the Massachusetts company that secured permission last year to build a payment system using the government-run network took the first step in rolling out its product.