Understanding and estimating the carbon dioxide emissions for urban buses at different road locations: A comparison...

Public transport buses are heavy-duty vehicles that travel through the city from morning till night, which emits a large number of greenhouse gases. Understanding and estimating the characteristics of carbon emissions for transit buses are critical in achieving a low-carbon transportation system. In this study, the changes in carbon dioxide (CO₂) emissions generated from new-energy buses as well as traditional diesel buses at bus stations, intersections, and road segments are compared using statistical analysis approaches; then the factors significantly affecting the emission rates are identified based on correlation analysis and feature selection methods. Finally, a gradient boosted regression tree (GBRT) model is proposed to conduct estimations for CO₂ emission rates of buses. The results indicate that different sensitivities to various influencing factors exist in the carbon dioxide emissions of different types of buses. In addition, the VT-Micro regression method and Random forest technique were utilized to compare with the developed GBRT model. According to the comparison results, the estimation errors of GBRT fluctuate in a smaller range, suggesting that the GBRT model outperforms traditional approaches in emission estimation of carbon dioxide. Also, the deep understanding of the emission characteristics for both new-energy buses and conventional diesel buses helps to plan and dispatch buses with different fuel types according to local traffic conditions.