Methodology for analysing vehicle trajectory and relation to geometric design of highways

With the increased emphasis on traffic safety in recent years, vehicle performance, in terms of speed, acceleration, braking, and cornering capabilities, has been improved through extensive research. As a result, driver behaviour has evolved greatly, and drivers expect better roads and higher design speeds. However, highway geometric design criteria in most design guides have not kept pace with these vehicle improvements. It is important to study the effect of geometric features of highways especially horizontal curves on driver behaviour. This will allow better design of highways and hence would improve traffic safety. The concept of highway design, with driver behaviour as one of its main parameters, has been gaining wider acceptance among highway professionals as an effective proactive tool to improve traffic safety. However, despite the importance of driver behaviour in vehicle and road design, and despite the work expended on this issue, a comprehensive understanding of driver behaviour is still lacking. The research in hand attempts to highlight points of deficiency in geometric design of highways that, through revision, could result in increased safety on roads. In doing so, data collected from a driving experiment are used to analyze driving behaviour, and an attempt will be made to incorporate the effect of driving behaviour to the geometric design of highways. This paper will mainly focus on driving behaviour data in terms of vehicle trajectory, steering angle, and rate of change of steering angle. The results are shown for different curves on two-lane two-way highways and freeways in Ottawa. The analysis shows that the results are promising and further analysis will result in improvements in highway design.