A remark on driver estimation of the time of collision with an oncoming car.

It is known that drivers tend to underestimate low speeds of oncoming cars while overestimating high speeds.In order to model driver behaviour when overtaking, or design an automated passing procedure, the time available before a potential collision is usually expressed in terms of initial distance between vehicles divided by their closing speed. It is shown that under certain conditions the observed interval of time given by this equation will tend to exceed the actual time.