Transit access effectiveness in American metropolitan areas

This research examines transit effectiveness empirically through the lens of access to employment. The approach uses the gradual shift of mobility to access to introduce the Transit-Walk Access Gap (TWAG) as an effectiveness indicator. TWAG is evaluated in the 50 most populated American Metropolitan Areas, and the analyses offer three conclusions. First, transit access effectiveness should not be measured in isolation of spatial and temporal dimensions of the transit service. The results show that transit service is slightly effective in short travel times, but a gradual improvement in transit access effectiveness is noticed by increased travel-time thresholds. Results also indicate that the spatial coverage of effective transit rises with an increase in travel time. However, the nature of the relationship does not appear to be linear. Second, transit access effectiveness is Central Business District (CBD) centric in most American metropolitan areas. The correlation analysis declares that transit access effectiveness declines from a surfeit of effectiveness to relative scarcity as one moves out from the center. It is realized that the correlation becomes more substantial with an increase in the travel-time threshold. Third, transit access effectiveness is positively correlated with transit ridership. The magnitude of association is a function of the metropolitan area and the travel-time threshold, with Memphis as the most elastic and New York the least elastic metropolitan area. The transit access effectiveness indicator introduced here should not be viewed as final. As transit access data are becoming increasingly available and as the goal of transport is shifting from mobility to access, further research needs to be conducted to advance the understanding of access-related transit effectiveness. The adoption of the indicator is, ultimately, a political process.