Taguchi-based impact analysis of highway geometric design and truck configurations on rollover and sideslip propensity

Horizontal curves on downgrades, commonly found in mountainous terrain, have higher crash rates and severity than tangents or pure curves. The lateral stability of tractor-semitrailers on such curves is a significant concern due to their heavy load, high center of gravity, and long-distance use. The combined impact of highway alignments and truck configurations has not been comprehensively studied due to data limitations. To address the high cost of experimental tests, a high-fidelity vehicle dynamics simulation model is used to investigate the rollover and sideslip propensity of tractor-semitrailers navigating curves on downgrades with varying geometric designs and truck characteristics. Lateral Transfer Ratio and side friction demand are used as criteria for rollover and sideslip stability, respectively. The multi-step Taguchi method is applied to identify the most influential factors on lateral stability. Results show that the tractor static toe angles (axle 1) have the most significant impact on sideslip stability, followed by tractor static toe angles (axle 2 & 3) and tractor yaw stiffness. The trailer height of load significantly affects rollover stability, followed by tractor axle 2 longitudinal distance and trailer static toe angle. Longitudinal slope has the greatest impact on rollover and sideslip stability, while the radius of the horizontal curve has the least effect. Focusing on these influential factors, rather than numerous tractor-semitrailer parameters, could aid in optimizing vehicle and highway design, as well as traffic control and management.