Time to Collision for Emergency Obstacle Avoidance

Time to collision is one of the indices to decide if a collision is avoidable. This paper presents the study on emergency obstacle avoidance from the viewpoint of time to collision. The times to collision at which the autonomous emergency steering has to be initiated to avoid a collision are derived for the five functions which are used for the generation of the emergency lane change paths. These functions are circular arcs, polynomial, ramp sinusoidal, sigmoid, and trapezoidal acceleration profiles. The times to collision at which the steering avoidance by using these functions has to be initiated are computed and compared. For a given lane change maneuver width of 3.5 m and coefficients of friction of 0.9, 0.5, 0.2, circular arcs give the shortest, and sigmoid gives the longest time to collision.