Can Time-To-Collision Decide the Braking Timing of the Driver?

In recent years, various new technologies to keep the distance to the lead vehicle have been introduced to prevent rear-end collisions or to improve maneuvering easiness. However, when the timing of automatic braking on the vehicle does not coincide with the driver’s timing judgment, he/she may feel uncomfortable. This paper examines which factor would mostly affect the driver’s judgment of braking timing by conducting indoor experiments using 12 participants. Various factors such as vehicle velocity, distance between two vehicles, relative velocity, time-to-collision (TTC), rate of change of visual angle and others were examined by discriminant analysis. We revealed that the rate of change of visual angle, which is the inverse of TTC, is mostly related to the driver’s judgment of braking timing instead of TTC which is popularly believed to have the important effect.