Estimating empirically the response time of commercially available ACC controllers under urban and freeway conditions

Research on Advanced Driver Assistance Systems (ADAS) and technologies that are expected to be involved in automated driving attracts lately a lot of interest from engineers and modelers. Adaptive Cruise Control (ACC) is one of the first automated functionalities available for privately owned vehicles and the deployment of such systems in public transport networks is constantly increasing. The impact of such controllers is still under investigation and there is a lot of discussion regarding their ability to positively affect congestion and pollution. In simulation studies regarding the impact of ACC on traffic flow, one key parameter is their response time. This parameter, usually takes low values, based on the controller's theoretical ability to respond instantaneously. In the preliminary results presented by the authors in [1] based on an empirical approach, it seems that this hypothesis is not valid. The present work builds on this conclusion presenting further results on two more commercially available controllers and testing their response in both urban and highway driving conditions under normal driving behavior without critical situations regarding the safety of the vehicle's passengers. The deployed ACC systems are primarily designed for safety and comfort. Adding on top of that the delays due to the interoperability of various vehicle systems, the final response time, that an observer would see, is very close to the human reaction time and this work shows that in some cases is even higher and by no means instantaneous. The findings here refer to normal driving conditions.