A novel route-based accessibility measure and its association with transit ridership

Transit systems play a key role in improving access to job opportunities and basic services such as health and education. Most studies in the literature calculate transit accessibility using traditional place-based indicators that measure accessibility at a given location. However, because transit routes are the main unit of analysis in most approaches for planning and operation of transit systems, these accessibility indicators provide limited information to inform transport planning at the route-level. In addition, previous studies have demonstrated the methodological limitations of traditional place-based accessibility metrics to study the association between accessibility and transit ridership. In this paper, we propose a novel route-based accessibility measure to fill the mentioned gaps. The indicator measures the average level of access to opportunities provided by a given transit route to the population in its extended catchment area. This indicator is flexible enough that it can be calculated using different travel cost functions and can be applied to measure access to different activity types for the whole population or for specific groups. To illustrate the applicability of the proposed indicator, we calculated the employment accessibility provided by all routes of the transit system of Fortaleza, Brazil. We also show that the proposed indicator has greater predictive power of transit ridership than other route-level accessibility measures found in the literature. This paper provides a methodological contribution that could help transport planners incorporate accessibility analysis into transit system redesign projects, and help practitioners anticipate what accessibility impacts and subsequent changes in transit ridership could be expected from route-level service changes, and to examine the influence of accessibility on transit ridership.