Abstract
This paper describes the experiments involving a driving simulator that examined the implicit relationship
between subjective perception and objective closeness of the gap between the host car and the lead car, the latter closing to the former at a constant relative velocity / at a constant relative deceleration rate. The subjective perception of closeness was quantified in terms of 1/TTC (θ?/θ, where theta is the driver’s visual angle of the lead car). The results suggest that the drivers perceive the lead car closing in terms of 1/TTC both in the constant relative velocity condition and the constant deceleration condition.