A Stopping-Distance Model for Driver Speed Decision Making in Curve Approach

One of the high priority research areas of the Federal Highway Administration is the development of the Interactive Highway Safety Design Model (IHSDM) that will allow highway designers to explicitly consider the safety implications of design decisions from the planning stage through the final design stage. The IHSDM will include a simulation model of driver/vehicle performance, which will contain a model for driver speed decision making as an important functional element. The speed decision model described in this paper requires two perceptual activities: (1) locate a target point a fixed radian distance into the idealized curve, and (2) estimate the stopping point given the current velocity and desired or current longitudinal deceleration. The control task becomes that of maintaining coincidence between the stopping and target points up to the point of curve entry. Correlation between model predictions and experimentally-observed trends of driver behavior is demonstrated.