Effects of geometric features of highway horizontal alignment on steering behavior of passenger car

In order to elucidate the effects of the features of horizontal curves on the steering behavior of passenger car, the vehicle driving behavior when negotiating simple curves (tangent + circular section + tangent) was investigated. A complete dynamic model of a passenger car was developed using the Automatic Dynamic Analysis of Mechanical Systems (ADAMS) software. Virtual driving tests were conducted on simple curves with different parameters for two driving patterns: curve cutting and lane keeping. Based on the variation in the amplitude of the angle input of the steering wheel, the steering process of a passenger car was divided into three stages: curve entry, maintenance, and curve exit. The steering lengths and steering times corresponding to the vehicle entering, remaining in, and exiting curves were obtained for each driving pattern. The relationship between the two parameters and the curve radius as well as that between the two parameters and the deflection angle was thus determined. On the one hand, this study can be a guide for selecting the parameters for curve geometry design and, in particular, for determining an appropriate value of the spiral length. On the other hand, the correspondence between the steering wheel angle and the trajectory curvature should allow one to identify the three driving states, namely, straight driving, variable-curvature driving, and circular-curve driving. This should help in improving driver behavior and hence driving safety.