Evaluating Alignment Consistency for Mountainous Expressway in Design Stage: A Driving Simulator-Based Approach

摘要

Evaluating design consistency is of great significance for safety evaluation on roadwaydesign prior to its construction. Conventional design consistency showed little considerationof driving performance due to the limitation in data availability. More importantly, they wereperformed only on the existing roads. In this study, a simulated driving experiment wascarried out in a high-fidelity driving simulator in Tongji University (Shanghai). A designstage four-lane (two-ways) mountainous expressway was implemented geo-based on thebasis of the detailed road design blueprint. We attempted to establish a practical approach forevaluating its design consistency through investigating operating speed consistency, vehiclestability and vehicle lateral offset (vehicle trajectory). Specifically, the speed consistency isstudied using the classic indicators – the 85th speed reduction and 85th maximum speedreduction. The vehicle stability was evaluated using lateral acceleration, rollover coefficientand the conventional side-friction parameter. In the lateral offset analysis, the adjusted lateraloffset was newly proposed, which is defined as the lateral offset from ideal vehicle trajectory.Utilizing the adjusted lateral offset can reflect the trajectory variation dependent on thecharacteristics of road geometry, which leads to the discovery of the inconsistencies in thestudied mountainous expressway. The lateral acceleration and rollover coefficient could beconsidered as supplementary measures to provide insights into drivers’ comfortableness aswell as the rollover risk. Another contribution of this work is that we developed predictingmodels for the considered consistency measures. The purpose is to better understand therelationship between driving performance and roadway geometry characteristics, as well as toprovide a practical formulation in a rigorous manner for road design consistency evaluation.