A study was made of the reactions of drivers who were impeded by an experimental car moving at constant slow speed on a single-lane road. The situation was arranged so that the 20 subject drivers were not aware that they were being observed. The photographic records indicated the distances of the drivers behind the experimental car over the 3-mile course. Three modes of driver response were noted: (a) avoidance, where drivers moved backward out of the influence of the experimental car, 10 percent of the drivers; (b) car- following, where drivers stayed close to the experimental car and did not execute large backward or forward movements, 30 percent of the drivers; and (c) a combination of avoidance and car-following, 60 percent of the drivers. Drivers' lead distance patterns did not conform to Herman's car-following equation. The equation may apply better to the situation where a driver reacts to disturbances introduced by the car in front. Drivers showed an indifference threshold. They accepted a range of positions behind the experimental car and reacted only when lead distance exceeded certain limits. A statistically significant resemblance was found in the driving patterns of operators who stayed close to the plant. This and previous studies suggest that the driver should be regarded as a strategist who continually adjusts his actions to fit his travel purpose and the road conditions he faces. He is not a stereotyped reacting element or "black box" to be simply described by a fixed equation. /author/
Abstract