In the design of Automatic Collision Avoidance Systems (ACAS) several thresholds exist which must be calibrated to ensure that the system both offers a degree of enhanced safety and mimics normal behavior. This paper examines driver behavior on motorways and urban roads in the U.K. in order to propose key parameters for such a system, in particular, an initiation threshold for deceleration and the subsequent deceleration. Data was collected using an instrumented vehicle on over two hundred drivers (6 subjects driving the test vehicle and 208 observed following the test vehicle during the course of the experiment). The data covered a wide range of speed between 5 and 120 km/h with more than 10 hours of time series data being collected. Data analysis has revealed a speed variant minimum observed Time-To-Collision that may be used for the activation of ACAS deceleration, and a multi-covariate general linear model has been developed using univariate analysis, to describe typical subsequent deceleration. The resultant system has also been examined through simulation in order to investigate the implications that such a system may have on a platoon of vehicles.
Abstract