Optimal fire station location for expressways integrating dynamic traffic accessibility and spatially heterogeneous fire risk.

OBJECTIVE: Expressway fire incidents are rising, yet dedicated fire stations remain largely absent, forcing reliance on urban services ill-suited to the linear, directional topology of expressways. Existing urban-oriented location models, assuming static travel times and uniform fire risk, fail to capture dynamic congestion and heterogeneous risk profiles in such confined environments. This study develops an optimization framework for expressway fire station siting that integrates dynamic traffic conditions and segment-level risk heterogeneity to minimize response delays and improve post-crash rescue accessibility. METHODS: In a case study of the Liuyang section of Hangchang Expressway, 1,495 demand points at 150-meter intervals and 10 candidate sites were identified. Fire rescue demand was quantified by combining dynamic travel times from the Baidu Maps API (24 daily intervals) and expert-assigned risk weights for tunnels, ramps, service areas, and general segments. A mixed-integer linear programming model maximized rescue demand satisfaction under constraints on station quantity (N = 1-6) and budget, with layouts solved via a branch-and-bound algorithm and evaluated using 10-minute response coverage as the primary indicator. RESULTS: With only existing urban stations (N = 0), no demand points (0%) were accessible within 10 min, most exceeding 30 min. Increasing new stations from 1 to 5 improved 10-minute coverage by 36.22 percentage points and reduced >30-minute points by 11.17 percentage points; marginal gains diminished beyond N = 5. Under a CNY 10 million budget, sites 6 and 7 were deployed, while CNY 20 million favored sites 4, 6, 7, and 8, achieving 39.26% coverage. With N = 3, a CNY 2.5 million budget increase shifted optimal sites from {2, 4, 7} to {4, 6, 7}, narrowing 20-30-minute response segments. Persistent > 30-minute gaps near certain interchanges stemmed from extended U-turn distances due to directional constraints. CONCLUSIONS: Static, urban-centric layouts are inadequate for expressways, leaving critical coverage gaps. The proposed framework integrates dynamic traffic conditions and heterogeneous risks, enabling resource-efficient siting. For the Liuyang corridor, five optimally sited stations offered the most cost-effective balance. This methodology provides a decision-support tool for authorities to rationalize emergency service layouts, expedite post-crash intervention, and enhance expressway safety.