Time-to-collision (TTC) provides a measure of crash risk or the time before impact if prevailing conditions continue. In this study, perceived TTC was examined with automobile drivers under realistic approach, rear-end crash scenarios conditions. A test track methodology was used. A total of 51 drivers ranging from 20 to 70 years old participated. The driver's vision was occluded at either 3.6 or 5.6 s TTC during an in-lane approach to a lead vehicle. Drivers provided TTC estimates by pressing a button the instant they felt that they would have collided with the vehicle ahead. Results indicated that TTC was consistently underestimated. The TTC ratio (perceived TTC/actual TTC) increased as driver speed decreased and as relative speed increased. Age, gender, actual TTC, viewing time and the presence of an eyes-forward mental addition distraction task had little significant effect on TTC ratio. The overall results indicate that under low TTC conditions, drivers estimate TTC in a relatively uniform fashion and that they are capable of providing this estimate based on a brief glimpse of the vehicle ahead. These findings are being applied in the development of an alert timing approach for a collision warning system.
Samenvatting