The Charlotte Area Transit System (CATS) operates the Lynx Blue Line light rail service in Charlotte and relies on automatic passenger counter (APC) data to report key ridership figures to the National Transit Database (NTD). In FY22, CATS evaluated the quality of its Lynx Blue Line APC data against a benchmark set by manual counts for NTD reporting purposes, but because APC data isn’t available for every train car on every trip, the Federal Transit Administration (FTA) requires agencies in these cases to describe the method and parameters used to estimate unlinked passenger trips (UPT) and passenger miles traveled (PMT), meeting prescribed levels of statistical confidence and precision with a signed review by a qualified statistician.
CATS engaged Foursquare ITP to estimate total and average UPT and PMT for weekdays, Saturdays, and Sundays by month. Foursquare ITP applied interpolation methods and data quality checks to the APC data, using an approach based on the National Center for Transit Research (NCTR) guidebook, Guidebooks for Estimating Total Transit Usage Through Extrapolating Incomplete Count, to interpolate missing trips in a statistically reliable way accepted by FTA.
The methods Foursquare ITP developed are also reusable for future reporting months and years. CATS submitted its NTD figures for UPT and PMT on time, with the confidence that a qualified statistician had reviewed and approved its interpolation methods.
Solutions and Outcomes
- Developed a new methodology to interpolate missing ridership data for trips without APC data.
- Conducted a thorough data quality review of APC data, including statistical tests of equivalence between APC counts and manual ridechecks.
- Led a qualified statistician’s review of the methodology, ensuring the results could be used for NTD reporting.