Driving Stability and Safe Speed Limits for Container Tractor–Semitrailers Under Strong Crosswinds

Strong crosswinds can critically destabilize high-sided container tractor–semitrailer combinations. This study integrates six-component force-balance wind-tunnel testing with a coupled aerodynamic and vehicle-dynamics framework to quantify aerodynamic loads, instability characteristics, and safe-speed boundaries under different road geometries. Sixteen aerodynamic cases combined vehicle speeds of 60, 80, 100, and 120 km/h with crosswind speeds of 19.0, 22.6, 26.5, and 30.5 m/s. The resulting aerodynamic loads served as inputs for 48 vehicle-dynamics simulations covering a level tangent, a −3% extended downgrade, and a curve with a 1000 m radius and 6% superelevation. As crosswind speed increased from 19.0 to 30.5 m/s, lateral force increased by 112.8%, 106.4%, 103.5%, and 96.4% at vehicle speeds of 60, 80, 100, and 120 km/h, respectively. Under unstable conditions, the minimum wheel load reached 0 kN and the maximum load transfer ratio (LTRmax) reached 1.00, accompanied by steering saturation and a sharp increase in yaw rate. The level tangent and downgrade exhibited identical discrete stability boundaries, with highest safe tested speeds of 120, 100, 100, and 60 km/h at the four crosswind speeds, respectively. On the curve, the highest safe tested speeds were 80 and 60 km/h at crosswind speeds of 19.0 and 22.6 m/s, respectively, whereas instability occurred even at 60 km/h under crosswinds of 26.5 and 30.5 m/s. The 20 km/h speed increments identify discrete stability boundaries rather than exact critical speeds. These findings provide a quantitative basis for differentiated crosswind warnings and dynamic speed management within the investigated conditions.