Experiments on estimating Time- To- Collision TTC values show that TTC is consistently underestimated. To evaluate driver use of TTC when actually taking evasive action, a field experiment was conducted where subjects approaching a stationary object were instructed to start braking at the latest moment they thought they could stop in front of the object. Results support the hypothesis that both the decision to start braking and the control of braking is based on TTC information available from the optic flow field.
Abstract