Research on Expressway Service Area Spacing in Mountainous Chongqing

Chongqing’s mountainous expressways face challenges of steep terrain, variable climate, and complex traffic demands, making service area planning crucial. This study proposes spacing strategies tailored to such conditions. Findings suggest service areas be placed every 30–50 km and parking areas every 20–25 km under normal circumstances. On freight-intensive sections with long downhill slopes and sharp curves, parking areas should be densified to every 15 km with added safety facilities. In terrain-constrained narrow zones, linear layouts, shared facilities, or interchange-based service areas are recommended, while relatively flat areas are suitable for independent dual-side layouts. The results indicate that a zoned, hierarchical, and flexible approach can enhance safety, meet user needs, and improve service quality. This research provides practical references for service area planning in Chongqing and other mountainous regions.