Visually-Guided Braking: the Optical Variables, Control Strategies and the Effect of Vehicle Dynamics

Abstract

This study aims to investigate the effects of vehicle dynamics, such as the braking function, on the optical variables and control strategies used in visually-guided braking. The task used in the study was to slow down from a high speed to stop before reaching an obstacle in the path of motion. Given this task, humans exhibit two different behaviors: impulsive braking and continuously regulated braking. The results of Experiment 1 indicated that, when the braking function was nonlinear, the weak version of the constant tau strategy was used in impulsive braking. The brake was initiated when the optical variable tau reached a critical value. When the obstacle was far away, the critical tau value was 3.7 s. When the obstacle was close, the critical tau value was 2 s. The aim of Experiment 2 was to investigate continuously-regulated braking. Experiment 2 revealed that, when the braking function was nonlinear, the participants exhibited predominantly impulsive braking and used the weak version of the constant tau strategy. The critical tau value used when away from the obstacle was 3 s, while the critical tau value used when close to the obstacle was 1.5 s. Taken together, the results of the present study indicate that a nonlinear braking function reinforces impulsive braking and suppresses continuously-regulated braking.