Combining speed and acceleration to define car users’ safe or unsafe driving behaviour

Abstract

Speed and acceleration describe the motion of a vehicle. Therefore, these parameters are fundamental to define the behaviour of a driver. To this aim, it is useful to analyse instantaneous and geo-referenced kinematic parameters of the vehicle recorded by real tests on the road.Among all the available methods in the scientific literature, a way for characterizing driver behaviour is the g–g diagram, that shows the longitudinal and lateral accelerations on the y and x-axes, normalized with respect to gravity, recorded on a vehicle during a real test on the road. However, we retain that also speed has to be considered for characterizing drivers’ behaviour, being acceleration and speed strictly interrelated. Starting from the g–g diagram, we propose a methodology which describes the relationship between lateral and longitudinal accelerations and speeds, and represents a tool to classify car drivers’ behaviour as safe or unsafe. An app for smartphone allows the geo-referenced kinematic parameters of the vehicle to be detected. The experimental survey supporting the methodology was carried out on a rural two-lane road in Southern Italy.