Minimizing costs and carbon emissions in railway alignment optimization: A bi-objective model

Railway alignment optimization should consider multiple environmental factors. Especially considering the changing climate, low-carbon design is crucial in alignment development. However, there is no reported study on alignment optimization considering life-cycle carbon emissions. To solve this problem, a model is proposed: (1) At the construction stage, carbon emissions generated by building material production and mechanical energy consumption are computed. (2) At the operation stage, train traction energy is converted into carbon emissions. (3) At the maintenance stage, carbon emissions generated by track replacement and structural maintenance are analyzed. (4) Moreover, the loss of carbon sink during a railway's life is estimated. Next, the above factors are integrated by an annual attenuation analysis for obtaining the total carbon emissions. This model is then combined with a cost function to establish a biobjective model and solved with a particle swarm algorithm. Finally, the model is successfully applied to a realistic railway case.