Improving Safety Using Adaptive Cruise Control to Prevent Truck–Car Rear-End Collisions

In the last decade, a growth has been registered in traffic flow and in the percentage of commercial vehicles especially on freeways. This increase creates problems not only from the point of view of congestion but also as regards safety. In traffic conflict an important role is played by driver behavior and capability, so new technologies can assist to prevent critical situations. In this context a study was carried out in order to estimate the safety effectiveness, in rear-end collisions, of Adaptive Cruise Control (ACC) on board of heavy vehicles Using specifications from two different trucks (medium and heavy load), a collision model was implemented under various operating conditions. The model considers a platoon of three vehicles traveling at constant speed: the leader is a car, the first follower a fully loaded heavy vehicle, the second follower another car. Considering probabilistic distributions for reaction time, tire performance and braking deceleration, various Monte Carlo simulations were carried out for different values of traffic speed, vehicle time gaps and pavement conditions, so as to calculate the probability of collision due to sudden braking of the leader car. Given the model assumptions, it was found that while equipping a vehicle with an ACC can significantly reduce the probability of a collision with the car ahead, it may adversely affect the safety of the cars behind. ACC safety effectiveness increases reducing the time gap between vehicles. Therefore to evaluate the actual inter-vehicle distances, an in field survey was carried out on a freeway.