Research on parking characteristics and layout optimisation in expressway service areas

The parking demand characteristics and facility layouts in expressway service areas (ESAs) differ significantly from those of urban parking lots; however, relevant studies on this topic remain limited. To address this research gap, this paper proposed a two-stage research framework to analyse ESA parking characteristics and optimise parking space allocation. In the first stage, a hierarchical structure consisting of parking lots, parking zones, and parking berths was developed to systematically examine the parking characteristics. In the second stage, a non-linear optimisation model was formulated to improve the spatial layout of parking spaces, with dual objectives of maximising the number of berths at varying geometrical angles and minimising the number of movements for a vehicle departing from the facility. The non-dominated sorting genetic algorithm II was employed to solve the model. A case study of Huanglishu Service Area in Nanjing, China, validated the effectiveness of the proposed framework. Numerical results demonstrated that the three optimised layout schemes enhanced parking capacities by 27.33%, 27.91%, and 31.98%, respectively, compared to the existing layout. These findings provide valuable practical insights for refining the planning of parking infrastructure and promoting sustainable development in ESAs.