The evolution of spatial equity of high-speed rail accessibility in China: An operation frequency based approach

The spatial equity of high-speed rail (HSR) accessibility in China has been a research topic for years. Most of current researches do not consider the impact of HSR operation frequency on accessibility. This study proposes an improved accessibility measurement taking frequency as an important factor and then analyzes the HSR accessibility and its spatial equity in China for the years of 2015, 2018, and 2021. Having defined spatial equity as the disparity of accessibility distribution, this study applies the Theil index to explore spatial equity and its changes over the three stages, as well as the regional difference among city groups based on geographical locations and administrative levels. The results demonstrated that the spatial distribution of HSR services accessibility in China was high in the East and low in the West. Only a few cities have the highest level of IAS (Improved Accessibility Score) which leads to a strong polarization in frequency-based accessibility. Spatial equity of accessibility has improved from 2015 to 2021, but HSR services developed more equally than HSR infrastructure networks from 2018 to 2021. When grouped by geographical locations, the West region has the worst spatial equity regarding IAS; however, the Northeast region has the worst spatial equity of OAS (Original Accessibility Score) in 2021. When grouped by cities' administrative levels, the group of provincial capitals has better spatial equity regarding IAS but did not have better spatial equity of OAS until 2021.