Calculating time-to-collision for analysing right turning behaviour at signalised intersections

Intersections are among the most dangerous places on the road network. Right-turn-against crashes, in countries with the left side traffic rule or left-turnagainst in other countries, are a major crash type occurring at intersections. Transportation researchers have utilised different conflict analysis methods to explore the influence of driver behaviours such as acceleration, deceleration, perception reaction time, gap acceptance, and stop/go decision at the onset of amber on right-turn-against crashes. However, there is no conflict technique that is sensitive to the different trajectories taken by the drivers turning right at intersections. This paper outlines a calculation method to estimate Time-To-Collision (TTC) for right-turn-against conflicts. In this method the curvature function of the vehicle trajectory is considered in the calculation formula. This enables the researchers to compare the risk of different right turning trajectories taken by the drivers at intersections. The calculation method has been applied to a signalised intersection in Melbourne, Australia and the results are interpreted.