Access Across America: Transit 2018 Methodology
Andrew Owen, Brendan Murphy
Report no. CTS 20-02
Accessibility is the ease and feasibility of reaching valued destinations. It can be measured for a wide array of transportation modes, to different types of destinations, and at different times of day. There are a variety of ways to measure accessibility, but the number of destinations reachable within a given travel time is the most comprehensible and transparent as well as the most directly comparable across cities. This report describes the data and methodology used in the Access Across America: Transit 2018 report, which examines accessibility to jobs by transit in 49 of the 50 largest (by population) metropolitan areas in the United States.
Rankings are determined by a weighted average of accessibility, giving a higher weight to closer jobs. Jobs reachable within ten minutes are weighted most heavily, and jobs are given decreasing weight as travel time increases up to 60 minutes.
This study estimates the accessibility to jobs by transit and walking for each of the United States? 11 million census blocks and analyzes these data in 49 of the 50 largest (by population) metropolitan areas. Transit is used for an estimated 5 percent of commuting trips in the United States, making it the second most widely used commute mode after driving. Travel times by transit are calculated using detailed pedestrian networks and full transit schedules for the 7:00 - 9:00 a.m. period. The calculations include all components of a transit journey, including "last-mile" access and egress walking segments and transfers, and account for minute-by-minute variations in service frequency.