Safe speed determination for emergency steering of heavy trucks on wet curved roadways
Current highway design standards employ point-mass models that neglect complex lateral load transfers during collision avoidance. To address this, an integrated analytical framework was developed to determine maximum safe operating speeds for heavy trucks executing emergency steering on wet curves. A modified bicycle model is formulated to explicitly capture roll kinematics, 3D road geometry, and axle-specific lateral load transfer. Safe speed thresholds are evaluated against visibility-limited collision avoidance trajectories, static rollover propensity, and individual axle friction limits. The Herrmann model is also incorporated to quantify rainfall-induced friction and visibility reductions. Validated via TruckSim simulations across 16 scenarios, the framework demonstrated high consistency with theoretical predictions. It successfully identified the limiting skidding axle with 87.5% accuracy while confirming sub-critical rollover margins. Sensitivity analysis reveals that geometric configurations—curve radius, superelevation, and center-of-gravity height—dominate lateral stability. Counterintuitively, varying heavy rainfall intensities (5–35 mm/h) induce less than a 2% fluctuation in threshold speeds, as lateral friction is primarily consumed by geometric demands. Thus, excessive speed relative to geometry, rather than precipitation-induced friction loss alone, primarily drives evasive instability. This framework provides a rigorous foundation for dynamic speed limit advisories and advanced driver assistance systems (ADAS) in adverse weather.