A Composite Index of Public Transit Accessibility

Measuring ease of access to transit services is important in evaluating existing services, predicting travel demands, allocating transportation investments, and making decisions on land development. A composite index to assessing accessibility of public transit is described. It involves use of readily-available methods and represents a more holistic measure of transit accessibility, integrating developer, planner, and operator perspectives. The paper reviews previous and current methods of measuring accessibility and selects three methods for application in a case study in Meriden, Connecticut. Inconsistencies are noted across the methods, and a consistent grading scale is presented to standardize scores. Finally, this paper proposes weighting factors for individual methods to formulate a composite measure based on individual accessibility component measures. The approach aims to provide a robust and uniformly applicable measure that can be interpreted easily by planners to identify shortcomings in service coverage and promote equity in transit accessibility in the community. Introduction Public transit is a key component of a sustainable transportation system that improves systemic mobility and can serve to mitigate the economic and environmental burdens that increased auto ownership can impose on the traveling population. Provision of public transit and infrastructure will not, in itself, fulfill public Journal of Public Transportation, Vol. 14, No. 2, 2011 70 transit’s potential. The system must be accessible and available to the community and its activity centers and connected with the rest of transportation system. In this paper, we consider accessibility to have three primary components: (1) trip coverage travelers would consider public transit accessible when it is available to and from their trip origins/destinations, (2) spatial coverage travelers would consider public transit accessible when it is within reasonable physical proximity to their home/destination, and (3) temporal coverage a service is accessible when service is available at times that one wants to travel. Another key aspect of public transit service is comfort, which addresses the question: “Is sufficient space available on the public transit at the desired time?” (Kittelson 2003). Hence, there is a need to assess and quantify public transit access considering the three aspects of public transit accessibility—trip, spatial coverage, and temporal coverage, along with comfort. Accessibility measures aid public transit operators and local authorities in the development of appropriate transit service expansion plans and policies by recognizing mobility needs and identifying service gaps. For assessing public transit accessibility in a region and the comparison of results with the existing methods, a consistent grading scale across the methods is warranted. Measures with consistent grading scales can facilitate the assessment of the distribution and quality of public transit service provided within an area, and a composite measure (properly weighted) can provide a single, representative measure. This paper proceeds with a literature review of existing transit accessibility measures, highlighting their scale of analysis and the measures used in their calculation. The Methodology section focuses on the three methods used in the development of the composite measure, which is then applied in a case study. The section also provides a standardized scaling option for comparison of the results. The Results section presents output of the comparative analysis and composite measure. The final section concludes the paper with a summary of major findings and some discussion on future adoption of the examined method to improve the performance of accessibility measures. Literature Review The attempt to develop public transit accessibility index has been discussed in several studies since the 1950s and continues to receive growing attention in transit sector (Schoon et al. 1999). Different measures have been designed to reflect dif-