Study on Route Alignment Adjustment and Optimization of Existing Road Resource Utilization in Highway Reconstruction and Expansion Projects

Abstract

This study develops a collaborative optimization framework for highway reconstruction and expansion that integrates “alignment adjustment–existing road utilization–functional improvement.” An evaluation indicator system is established to assess the utilization value of existing road resources, covering geometric alignment resources, structural resources, land-use resources, traffic organization, economic benefits, and environmental benefits. The weights of the indicators are determined by combining the analytic hierarchy process and the entropy weight method. On this basis, a multi-objective alignment optimization model is proposed, incorporating engineering cost, traffic safety, existing road utilization, ecological impact, and life-cycle carbon emissions, and the model is solved using the NSGA-II algorithm. A reconstruction and expansion project of a mountainous Class II highway in Tibet is taken as a case study for verification. The results show that the comprehensive coordination scheme achieves the lowest comprehensive evaluation value of 0.28 under the conditions of an existing road utilization rate of 64.2%, a safety risk index of 0.31, and carbon emissions of 118,000 t, outperforming both the existing-road-priority scheme and the alignment-improvement-priority scheme. The findings indicate that embedding the value assessment of existing road resources into the entire process of alignment adjustment can effectively improve the scientific basis of alignment decision-making, enhance resource utilization efficiency, and promote green and low-carbon development in highway reconstruction and expansion projects. This study provides methodological support for optimizing highway reconstruction and expansion schemes under complex constraints.