This paper describes the results of a test program to evaluate various roadway disturbances present in the driving environment. The specific objectives were to pare down the list of possible roadway disturbances to the worst cases, identify handling problem areas, find meaningful response parameters and compare responses of different vehicles which might influence the results.
The program provided an accident data analysis, survey questionnaire results and full scale test results which found the pavement/shoulder dropoff (requiring an edge climb maneuver) to be the most severe and most likely disturbance to result in lane exceedance. This occurs when the vehicle is scrubbing one set of tires on the shoulder edge (or encountering the edge at too shallow an angle for climb), thereby climb), thereby requiring the driver to apply a large steering deflection to get the car to climb back onto the pavement. In this case the vehicle will “spin out” if the speed is high enough.
Road tests were performed with four passenger cars in an attempt to obtain objective vehicle response performance measures as a function of vehicle type, shoulder height and tire parameters (construction, wear and pressure). The tests were divided into two categories: closed loop and open loop. In the closed-loop tests the effects of the driver, the vehicle, and the environment were all included, whereas in the open-loop tests only the basic vehicle response to the shoulder climb was considered. Results derived from these test procedures are discussed in the paper.