Optimal Speed Model of Urban Underwater Tunnel Based on CO2 Emissions Factor

Abstract

This study aims to reduce air pollution caused by vehicle emissions in confined spaces and realize low-carbon travel in urban underwater tunnels. Based on the MEET (Methodologies for Estimating Air Pollutant Emissions from Transport) and COPERT (Computer Programme to Calculate Emissions from Road Transport) models, combined with real vehicle test data, an urban underwater tunnel speed–CO2 emissions factor model was constructed. Results show that: Different working conditions have a great impact on the MEET model; load and slope factors expand the actual CO2 emissions factor, which is different from the actual situation. The CO2 emissions factor in the COPERT model is negatively correlated with the speed, and there are fewer variables in the model, so the parameters are more controllable and more in line with the actual situation. According to the vehicle gasoline consumption and taking CO2, i > GC as the judgment index, the optimal limit speed of the ramp is calculated to be 40 km/h, while the main line maintains the existing state of 60 km/h. The model is simple and easy to operate, can be applied to estimate vehicle CO2 emissions factor at underwater tunnels in other cities, providing a basis for traffic management and effectively realizing low-carbon travel.