Evaluation of ACC vehicles in mixed traffic: lane change effects and sensitivity analysis

Almost every automobile company is producing vehicles with adaptive cruise control (ACC) system onboard that enables a vehicle to do automatic vehicle following in the longitudinal direction. The ACC system is designed for driver´s 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 by acting as filters of a wide class of traffic disturbances. It has been argued 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 all vehicles had been manually driven. In this paper, we examine the effect of lane changes on the benefits suggested by Bose and Ioannou as well as the sensitivity of these benefits with respect to various variables such as the penetration of the ACC vehicles, 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 a cut-in or an exiting vehicle in a way that is beneficial to the environment when compared with similar situations where all vehicles are manually driven. We concluded that a higher number of possible cut-ins that may occur due to the larger gaps created during high-acceleration maneuvers by the vehicle in front of the ACC vehicle, will not annul the benefits obtained 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.