Research on the optimal selection of route design schemes for mountainous expressway based on EWM-TOPSIS coupling

Selecting a perfect route for a mountainous expressway at the design stage is often challenging because multiple feasible alternatives must be compared under competing objectives. A quantitative evaluation framework to support mountainous expressway alignment decision-making is proposed in this study. Eighteen indicators were identified from 4 dimensions—project scale, technical standards, economic benefit, and environmental benefit. Indicator weights were determined using the entropy weight method (EWM), and the resulting weights were integrated with the technique for order preference by similarity to an ideal solution (TOPSIS) to establish a comprehensive alignment selection model. The relative merit of each alternative was evaluated by comparing its distances to the positive and negative ideal solutions. The proposed method was applied to an actual mountainous expressway project with 4 candidate alignment schemes. The results show that: (1) EWM reduces the influence of subjective preference in weighting and enables a more objective indicator system, while TOPSIS provides a transparent quantitative ranking of the alternatives; and (2) sensitivity analysis demonstrates that the C13 scheme consistently ranks first across ten perturbation scenarios, indicating strong robustness, and it is therefore identified as the preferred design alternative because it is relatively short, achieves the best technical standards, has the highest project cost, and provides relatively good environmental benefits with moderate house demolition requirements. The proposed EWM–TOPSIS coupling approach represents a practical multi-attribute decision-making tool that combines quantitative and qualitative considerations and can inform alignment scheme selection in comparable infrastructure projects.