Phased Planning of Expressway EV Charging Infrastructure: A Data-Driven Systems Approach Considering Spatial Heterogeneity and Peak Demand

Planning charging facilities at expressway service areas requires joint consideration of traffic growth, charging behavior, temporal demand peaks, charger technology, existing equipment, and local power-supply capacity. However, existing planning approaches rarely integrate spatially heterogeneous charging behavior, peak-demand effects, charger-technology transition, existing infrastructure, and electrical-capacity constraints within a unified phased planning framework. This study develops a data-driven phased planning method that combines EV traffic forecasting, station-specific charging probability, peak-hour and holiday demand correction, charger-specific service rates, existing-capacity comparison, and transformer-capacity screening. Operational records from 2021 to 2024 were used to calibrate the main parameters for a provincial expressway network in China covering approximately 6000 km and 212 service areas. A baseline planning scenario and six single-parameter sensitivity cases were evaluated. Charging probability varied from 0.3% to 20.9%, with a network-weighted mean of 5.73%, demonstrating substantial spatial heterogeneity among service areas. Under the baseline scenario, the required network capacity reaches approximately 4520 conventional fast chargers and 1230 ultra-fast chargers by 2030, while the share of ultra-fast chargers in annual additions increases from 37.5% in 2025 to 86.9% in 2030. A retrospective comparison across 111 service areas yielded an overall discrepancy of approximately 15.5% and was interpreted as an engineering consistency assessment rather than independent predictive validation. Sensitivity analysis showed that EV traffic growth and the penetration of ultra-fast-compatible vehicles have the greatest influence on projected ultra-fast-charger requirements. The proposed framework provides a practical basis for differentiated and periodically updated expressway charging-infrastructure planning as traffic demand, charging behavior, vehicle technology, and electrical capacity evolve.