Variable Speed Limit On Circular Curve Road Sections In Mountainous Area Based On Vehicle Dynamic Safety Boundary Theory

The rapid development of the mountainous highways enhances the overall technical level of China's road network during recent years. Vehicle instability, such as sideslip, loss of steering, often occurs under adverse weather in road sections with complex three-dimensional alignments, especially in the road sections with circular curves. Therefore, it's necessary to design proper speed limits to ensure traffic safety.In this dissertation, the speed limits were determined by vehicle dynamic safety boundaries which consist of lateral safety boundary based on the energy method and longitudinal safety boundary based on AASHTO model under a certain visibility and road adhesion coefficient. Integrated with the Fiala-Qiaoshi nonlinear tire model and driver preview optimal curvature model, a driver-vehicle-road closed-loop system was developed, taking lateral, yaw and roll movement of vehicle body into account. Then the vehicle dynamics simulations were carried out in MATLAB/Simulink. The influence rule of superelevation, radius and road attachment coefficient on vehicle driving safety on circular curve road sections was investigated and consequently the critical vehicle speeds of cars and trucks were determined. Finally, the comparisons with methods in previous literatures were made to analyze the superiority and scope of application of the proposed method.