Comparison of carbon emission intensities across different urban passenger transport modes
To compare the carbon emissions levels across various urban passenger transport modes,we proposed a comprehensive evaluation index and developed a detailed calculation model for urban passenger transport carbon emission intensity.Through the application of Kruskal-Wallis test and Bonferroni correction,we discemed significant variances in carbon emission intensities among different urban passenger transport modes.Additionally,the k-means clustering method was further employed to examine the carbon emission intensity across urban rail transit(URT)of different operational mileages.The findings revealed:(1)Both RPCF(Rated person-kilometer carbon emission factor)and APCF(Actual person-kilometer carbon emission factor)indicators were effectively to assess the carbon emission intensity of urban passenger transport modes,yet a significant and non-negligible difference between these two indicators was observed.(2)When average levels of RPCF and APCF were examined,urban public transport was shown to have a clear low-carbon advantage over private transport.The average values of RPCF were determined in descending order for gasoline cars,electric cars,diesel buses,natural gas buses,URT and electric buses,recorded as 40.69,21.26,14.86,11.63,8.81 and 5.28gCO2/(person·km)respectively;whereas APCF averages were identified in descending order for gasoline cars,electric cars,URT,diesel buses,natural gas buses and electric buses,noted as 113.02,59.06,43.14,42.47,33.24 and 15.07gCO2/(person·km).Compared to RPCF,the low-carbon advantage of URT's APCF was diminished.(3)URT and diesel buses were not observed to have a low-carbon advantage over electric cars.Natural gas buses and electric buses exhibited a significant low-carbon advantage compared to URT,with electric buses being identified as the most carbon-efficient mode and gasoline cars as the least.(4)URT with higher operational mileage was shown to have a greater low-carbon advantage compared to that with lower mileage.URT with operational distances of 0~70,70~200,200~400,400~600 and 600~800 km had their APCF measured as 86.03,57.43,51.71,34.11 and 33.41 gCO2/(person·km).