ABSTRACTIn order to maintain the sustainability of High Speed Railway (HSR), it is important to understand total and region-specific long-term demand. Our study targets the eight HSR stations that have been in operation in Taiwan since 2007. As the service itself has not undergone major changes, we examine the impact of other demand and supply factors in order to explain demand growth over time in consideration of regional heterogeneity. We focus on the effects of station accessibility as well as its impact on demand via usage ‘adoption rates’. The latter is related to product diffusion theory. By using monthly ridership data, we calculated yearly regional ‘adoption ratios’ to describe the spread of THSR usage. Our results show that regional heterogeneity in adoption ratios exist and influence its HSR demand pattern. We also discuss that station accessibility by transit is an important factor to understand long-term HSR demand developments. We show that initial bus services (shuttle bus and bus rapid transit (BRT)) influence demand in the short and long term. Taking the findings together, we suggest that therefore improving access modes, has positive impacts to short- as well as long-term HSR demand and require careful consideration by decision makers.