1. A system for assisting a driver operating a vehicle traveling on a road, the system comprising: an engine controller regulating operation of an engine of the vehicle to provide a desired engine output characteristic; control logic that controls the engine controller to modify the engine output characteristic in response to at least one of a detected state of an environment around the vehicle and a determined risk; and an accelerator having different positions and selectively producing different acceleration reaction force characteristics, each different acceleration reaction force characteristic providing varying of reaction force with different positions of the accelerator.