Operating speed characteristics of heavy vehicle on expressway uphill section

The traffic composition, heavy vehicle power, load mass and mass-to-power ratio of expressway in Inner Mongolia were analyzed, and the typical vehicle on expressway uphill section was determined. Based on the corrected speed prediction model, the operating speed curves of typical vehicle under different slope gradients (1%-6%), slope lengths, load masses (30, 40, 50, 55 t), mass-to-power ratios (80, 120, 160, 200 kg·kW^-1) and initial speeds into slope (0, 20, 40, 60 km·h^-1) were drawn, and the reasons of curve changes from vehicle dynamics perspective were studied. Analysis result shows that Foton Auman ETX9 heavy truck is the typical vehicle on the expressway for coal transportation in Inner Mongolia. When heavy vehicle runs on a certain slope, the vehicle speed will not decrease with the increase of slope length after reaching balancing speed. The bigger the slope gradient is, the faster the vehicle speed drops, the lower the final balancing speed is. The bigger the load mass is, the faster the vehicle speed drops. The smaller the mass-to-power ratio is, the better the vehicle climbing performance is. The higher the initial speed is, the longer the distance for vehicle to reach balancing speed is.