Transit authorities reporting to the Federal Transit Administration (FTA) provide data on the number of passengers who board public transportation vehicles rather than the number of passengers they serve. Passenger boardings are called unlinked and linked passenger trips. Unlinked trips are total boardings on an individual vehicle. Linked trips refers to the total number of riders and measures the actual number of complete trips from origin to destination, including transfers. Unlinked trips are viewed as a measure of transit utilization (at the system, route, or subroute level), while linked trips are used to measure revenue passengers. The ratio of unlinked to linked trips indicates the relative usage of transfers in the transit system . Determining the actual number of passengers using a transit system can be a difficult task because of the tracking requirements for the number of transfers from one vehicle or mode to the next, from one agency to another, and from the use of day passes and cash.
Because FTA does not have an official methodology for estimating the actual number of passengers that ride transit systems, individual transit agencies develop their own passenger counting and estimation methodology based on their resources and local attributes. Individual transit agencies may estimate the actual number of passengers based on a variety of methods and data-collection tools to help control for double counting, such as, automatic passenger counting units, on-board surveys, manual people counters, video camera tracking, and fare box analysis.
The American Public Transportation Association (APTA) made an estimate, based on an average weekday, of the actual number of passengers carried by member authorities in 2000. APTA concluded that the number of people using the national transit system is 45 percent of the number of total unlinked trips reported or 14 million people, based on an average of 32.9 million daily unlinked weekday trips. This estimate reflects the average travel patterns of approximately 50 percent of all transit riders who take 2 trips per day between home and employment and those dependent on transit who could take up to 10 trips per day .
1. American Public Transportation Association, Public Transportation Fact Book 2003 (Washington, DC: February 2003).
2. Boyle, D.B., “Passenger Counting Technologies and Procedures,” TCRP Synthesis of Transit Practice 29 (Washington, DC: Transportation Research Board, 1998).