Sunday, August 7, 2011

Transportation Requirements: Reliability

One requirement of any transportation system is that it be reliable--absent reliability, people on inflexible schedules who have a choice of transportation mode won't choose public transit. In order to test the reliability of public transit in northern Virginia, we used an Apple iPhone with GPS enabled to capture (see photos below) the arrival times on four randomly selected stops served by the Fairfax Connector.

How reliable is public transport in Northern Virginia? In our sample, the best arrival was one minute late, the worst was 11 minutes late, with a seven minute average. When routing passengers with connections, the local transit Route Planner builds in five minutes between arrival of one segment and departure of the next segment, which means with this seven minute average delay, most connections would be missed. While this sample size is too small to give any confidence in the level of system reliability, a seven minute delay is a cautionary indicator that calls for closer examination.

Date.time (yymmdd.hhmm)LatLongStopScheduledRouteLate?
110805.113338.9165, -77.220667Tysons Corner Shopping Center11:32FC4021
38.895667, -77.225
Gallows Rd & Elm Pl20:54FC4018
38.916333, -77.221333
Tysons Corner Shopping Center20:59FC4018
110806.223338.914333, -77.221667Tysons Corner Shopping Center20:22FC40211

- Stuart M. Whitaker

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