Brian S. Repa

Driver steering reaction time to abrupt-onset crosswinds, as measured in a moving-base driving simulator.

A moving-base driving simulator was used in three experiments involving driver reaction time (RT) to simulated crosswind disturbances. Analyses were conducted on driver steering reaction time (RT) to the disturbances. Experiment 1 revealed that RT was significantly shorter when physical-motion cues were present. A second variable, vehicle yaw rate rise time, showed no effect. In Experiment 2, design parameters influencing aerodynamic behavior of a vehicle were adjusted. RT increased as the vehicle center of pressure (point of crosslvind application) moved rearward (rom the (ront axle. However, rearward movement of the center of pressure also produced less disturbance of the vehicle itself Changes in understeer and steering sensitivity yielded no significant effect. In Experiment 3, both uninitiated drivers and drivers with time on task were examined. Neither the first exposure to a step gust nor driving time up to 150 mirl caused significant changes in RT when perfurmance was compared with that of practiced, fresh drivers. Interexperiment comparisons using crosswind amplitude and shape as independent variables demonstrated that the amplitude and rise time of the crosswinds were critical determinants of steering RT.

EVALUATING THE DRIVING POTENTIAL OF THE HANDICAPPED USING A SIMULATOR

The GMR Driving Simulator was used to study the performance of four teen-aged, novice drivers, two of whom had cerebral palsy. The purpose of this pilot study was to determine the potential of the simulator to discriminate between the driving abilities of medically handicapped and non-handicapped individuals. The study concentrated on the psychomotor aspects of lane-keeping performance in the presence of road curvature and environmental disturbances. The study indicates that a dynamically realistic driving simulator could be a valuable screening device for indentifying potential performance difficulties in handicapped individuals prior to behind-the-wheel instruction.

The Influence of Vehicle Aerodynamic and Control Response Characteristics on Driver-Vehicle Performance

The effects of changes in understeer, control sensitivity, and location of the lateral aerodynamic center of pressure of a typical passenger vehicle on the drivers opinion and on the performance of the driver-vehicle system were studied in the moving-base driving simulator at Virginia Polytechnic Institute and State University. Twelve subjects with no prior experience on the simulator and no special driving skills performed regulation tasks in the presence of both random and step wind gusts. The lower weights and moments of inertia of future passenger vehicles can be expected to change the effect of wind gusts making the evaluation of aerodynamic and control response characteristics on closed-loop wind disturbance regulation a matter of increased interest.

STUDY OF VEHICLE STEERING AND RESPONSE CHARACTERISTICS IN SIMULATED AND ACTUAL DRIVING

Simulator characteristics were matched to those of the full-scale vehicle with respect to steering torque gradient, control sensitivity, and lateral acceleration response time; identical disturbance signals were applied to each facility. The influence of torque gradient was accentuated in the Simulator and at low levels of control sensitivity, with high levels of torque gradient producing smaller steering wheel and vehicle motion deviations. The effect of control sensitivity on steering wheel deviations was accentuated under actual driving conditions and for slower response times. A greater improvement in lateral position deviations with increased control sensitivity was noted for the slow response time configurations. Even though there were statistically significant interactions involving simulated versus actual driving conditions, examination of the data indicates that the performance trends are essentially the same in both facilities.