Xuesong Wang,Ting Wang,Xinwei Wu
Abstract: Horizontal curve combined with vertical alignment is a typical component of freeway in mountainous areas. There’s no quantitative standard of each element on combined alignment in current Chinese standards. Improper combination might cause serious safety problems in operation. Attention has been paid on correlation between combined alignment and accident data using statistical models. But quantified indices regarding horizontal curve combined with vertical alignment have not been established. Skid and rollover are significant threats to vehicle safety, mainly caused by excessive lateral acceleration. Correlation between lateral stability and combined alignment has been investigated based on real world experiments. The sample of the real world experiment is limited and the driving environment cannot be controlled for research purpose. Therefore, it is difficult to quantify the influence accurately based on real world experiments. It’s urgent to use a better approach to quantify the influence of horizontal curve combined with vertical alignment on lateral stability. For this study, an experiment was carried out on Tongji University’s 8 degree-of-freedom driving simulator. Bayesian multiple linear regression models were developed to quantify the correlation between lateral acceleration and the alignment elements. Results suggest that vehicle lateral acceleration is significantly affected by horizontal curve radius on all combined sections while other factors have varying degrees of influence on different types of combination segments. Based on the regression models, safe domain analysis was conducted to provide appropriate quantitative index of each element.Results indicated that minimum of horizontal curve was different on different combined segment.