Research on Maximum Longitudinal Slope and the Length Limit of Expressways Based on the Performance of Pure Electric Heavy-Duty Vehicles

With the global energy transition and advancements in electric vehicle technology, the use of pure electric heavy-duty vehicles in logistics is rising. However, current highway grade design standards do not fully consider their performance characteristics, making it urgent to establish appropriate grade limits. This study aims to explore the maximum grade and the critical length suitable for pure electric heavy-duty vehicles on highways. A co-simulation platform for pure electric heavy-duty vehicles was built using TruckSim and MATLAB/Simulink. A comparative analysis was conducted on the climbing characteristics of pure electric heavy-duty vehicles and traditional fuel-powered vehicles. Additionally, the climbing speed decay degree (DV) was introduced to investigate the speed variation characteristics of pure electric heavy-duty vehicles under the joint influence of multiple factors. These findings serve as the basis for determining the maximum grade and the critical length applicable to pure electric heavy-duty vehicles on highways. The research findings indicate that, compared to traditional fuel-powered heavy-duty vehicles, pure electric heavy-duty vehicles exhibit smoother acceleration and deceleration processes, smaller speed fluctuations, higher travel speeds, and greater equilibrium speed values during uphill climbing. The power-to-weight ratio has a greater impact on the climbing speed of pure electric heavy-duty vehicles, while the initial vehicle speed has a relatively minor effect. It was observed that the dynamic performance of pure electric heavy-duty vehicles does not align with the maximum grade stipulated by current regulations in China. These research findings provide important reference points for road longitudinal section design and vehicle management in road freight enterprises.