Measurement of effective transit supply index between OD pairs

Public Transit (PT) Supply Index (SI) is primarily estimated to prove the differences in demand and supply to provide an understanding of social issues related to PT, such as equity, and social inclusion. The definition of SI is yet not clear from the literature; thus, it is usually mixed with accessibility, and availability of transit service. This study revisits the supply index estimation problem with the more detailed and robust approach. A route-based equation is developed in which the variables include walk buffer areas of stops, the total area of the zone, straightness of route provided to that zone, and average Available Seating Capacity (ASC) of transit services. The equation provides Origin-Destination (OD) based SI, that is SI for each OD pair. Furthermore, the equation also incorporates the number of transfers needed to travel from the origin zone to the destination zone and speed between those zones. Most of the data required for analysis are taken from either static Google Transit Feed Specifications (GTFS) or smartcard data. Though the analysis is only carried out at a few OD pairs, when the method is applied to all zones it is expected to provide detailed insight into the transit supply, therefore can be helpful for planners to visualize and improve the complex and cumbersome networks in a more effective manner.