A driver assistance system for a vehicle includes at least one forward viewing camera and a control having an image processor operable to process image data captured by the forward viewing camera. The vehicle includes start-stop technology operable to turn off the engine of the vehicle when the vehicle stops and operable to restart the engine of the vehicle to enable the vehicle drive forward. Responsive at least in part to processing by the image processor of captured image data, the driver assistance system determines that the vehicle, when stopped, is behind a stopped leading vehicle. Responsive at least in part to processing by the image processor of captured image data, the driver assistance system determines forward movement of the leading vehicle from its stopped position. Responsive at least in part to the determination of forward movement of the leading vehicle, the control automatically restarts the engine of the vehicle.