After Noah drops off Alison at the Lockhart home and starts up his van to drive away, the instrument cluster can be clearly seen through the passenger window and the RPM gauge does not move when you hear the sound of the engine starting.
Alison takes off with her bike and makes a left out of The Lobster Roll, which is towards Amagansett, not a right, which is the way to go to Montauk from that restaurant.