Impact of high-speed rail on road traffic and greenhouse gas emissions

Intercity high-speed rail (HSR) can have large climate benefits with its high energy efficiency. This study explores the substitution effects of HSR on road traffic in China, which can be translated to an annual reduction of 14.76 million tons of CO2-equivalent emissions. Carbon emission reduction in the transportation sector is essential in the global mitigation effort, and a large-scale public transport system has the potential to be an effective instrument. High-speed rail (HSR) is one such example, yet it is unclear how much reduction in road traffic results from new rail routes. Using the difference-in-differences method, we show that new HSR routes in China lead to a 20.5 log-point reduction in the number of passenger vehicles and a 15.7 log-point reduction in freight vehicles running on parallel highways. These reductions were not seen on ordinary national roads. These effects translate into an annual reduction of 14.76 million tons of CO2 equivalent of GHG emissions or 1.75% of GHG emissions in China's transport sector. This mitigation effect mainly comes from the substitution of highway goods transport with the conventional railway instead of the direct replacement of highway passenger transport with HSRs. The environmental benefit of HSR in China has not been fully realized because of the thermal-dominated electricity supply. Our further projections suggest that in greener electricity conditions, the HSR in China can substantially contribute more to the reduction in GHG emissions from the transport sector.

Automated summary

The study shows that the construction of new high-speed rail routes in China has a significant impact on reducing road traffic and carbon emissions, primarily through substitution effects. The environmental benefits mainly come from replacing highway goods transport with conventional railways, and it is projected that under greener electricity conditions, high-speed rail in China can contribute even more to reducing greenhouse gas emissions in the transport sector.