California Partners for Advanced Transportation Technology

Almost every automobile company is producing vehicles with Adaptive Cruise Control (ACC) systems that allow a vehicle to do automatic vehicle following in the same lane. The ACC system is designed for driver comfort and safety and to operate with manually driven vehicles. These characteristics of ACC were found to have beneficial effects on the environment and traffic flow characteristics [1, 2, 3] by acting as filters of a wide class of traffic disturbances. It has been argue that the smooth response of ACC vehicles to high acceleration disturbances or large position errors creates large gaps between the ACC vehicle and the vehicle ahead inviting cut -ins and therefore generating additional disturbances that would not have been created if the vehicles were all manually driven. In this report we examine the effect of lane changes on the benefits suggested in [1,2,3] as well as the sensitivity of these benefits with respect to various variables such as ACC penetration, level of traffic disturbances etc. We demonstrate using theory, simulations and experiments that during lane changes, the smoothness of the ACC vehicle response attenuates the disturbances introduced by the cut -in or exiting vehicle in a way that is beneficial to the environment when compared with similar situations where the ACC vehicle is absent. We concluded that the higher number of possible cut-ins that may be present due to the higher gaps created during high accelerations maneuvers by the vehicle in front of the ACC vehicle, will not take away the benefits shown in the absence of such cut -ins when compared with the situation of similar maneuvers but with no cut-ins in the case of 100% manually driven vehicles. Keywords: Adaptive Cruise Control vehicles, manually driven ('manual') vehicles, mixed traffic, vehicle following, lane change, air pollution, fuel consumption.