What determines the real-world CO2 emission reductions of ridesplitting trips?

Abstract

Ridesplitting has great potential to alleviate the negative impacts of ridesourcing on the environment. However, not all ridesplitting trips are effective in reducing CO2 emissions. The actual trip-level environmental impact of ridesplitting and its determinants remain unclear. To bridge this gap, this study reveals what determines the real-world CO2 emission reductions of ridesplitting trips based on the observed data of ridesourcing services in Chengdu, China. First, the CO2 emission reduction of each ridesplitting trip compared with its substituted single rides is calculated using a vehicle emission model (COPERT) coupled with GPS trajectory data. Then, four implementations of gradient boosting machines, namely GBDT, XGboost, LighGBM, and CatBoost models, are employed to explore the relationships between the ridesplitting CO2 emission reduction rate and its explanatory variables. Finally, the nonlinear and interaction effects of these variables are analyzed based on partial dependence plots and SHapley Additive ExPlanations. Empirical results show that the ridesplitting CO2 emission reduction rate varies from trip to trip, with an average of 43.15 g/km. In the real world, approximately 15 % of ridesplitting trips even increase CO2 emissions, mainly due to the low overlap rate and high detour rate of the shared rides. To enhance the CO2 emission reduction rate of ridesplitting, the overlap rate, number of shared rides, average speed, and ride distance ratio should be increased, while the detour rate, actual trip distance, and ride distance gap should be decreased. This study can help the ridesourcing companies better match the shared rides and improve the environmental benefits of ridesplitting.