Beyond Access: A Grid-Based Framework for Measuring Service Levels and Inequity in Multimodal Public Transit

Abstract

Conventional transport studies, focused on accessibility, often fail to capture the actual service levels and spatial inequity of public transport. This study develops a novel grid-based multimodal multiplex network framework for South Korea to overcome these limitations. Using nationwide GTFS data, the authors model each transport mode as a distinct layer on a 1 km² grid, incorporating service frequency as a weighting factor to measure service levels. The analysis reveals extreme spatial polarisation, with service levels concentrated in metropolitan cores while extensive non-urban areas experience severe service deprivation. The proposed framework provides a robust and precise tool for diagnosing transport inequity and offers evidence to support policies aimed at creating a more inclusive and sustainable public transport system.