Changes in low-carbon transportation efficiency of Chinese roads after considering the impact of new energy vehicles

China aims to attain peak carbon emissions by 2030 and achieve carbon neutrality by 2060. As a top-ranked carbon-emitting industry, the transportation industry faces a severe low-carbon transformation situation. The rapid development of new energy vehicles (NEVs) has become an important means to improve the low-carbon transportation efficiency of Chinese roads. Existing studies rarely consider the impact of the development of NEVs, and a regional imbalance exists in the development of low-carbon transportation in China. This study takes the sales of NEVs as an important exogenous variable and uses a modified meta-dynamic non-radial directional distance function (DDF) to analyze the low-carbon transportation efficiency of Chinese roads. After incorporating the sales of NEVs into the analysis system, China's overall road transportation efficiency has significantly improved. The present value of the average annual low-carbon transportation efficiency has increased by 0.06–0.1 compared to the original value, but there are regional differences. The eastern region, with its technological advantages, has achieved the best performance with an average low-carbon transportation efficiency of 0.92. The substitution of NEVs has significantly improved the efficiency of low-carbon transportation on roads in central China. The improvement of low-carbon transportation efficiency on roads in western China is limited due to factors such as the low popularity of NEVs. We delved into the reasons for the development of NEVs to improve the efficiency of low-carbon transportation on roads, discussed the improvement of carbon emissions through the promotion of NEVs, analyzed the regional imbalance of low-carbon transportation efficiency on roads, and provided policy recommendations for the future development of NEVs from the perspective of regional differences.