Caltrain is a commuter rail transit system that serves the San Francisco Peninsula and the Santa Clara Valley in the U.S. state of California. It is operated under contract by TransitAmerica Services and funded jointly by the City and County of San Francisco, San Mateo County Transit District (SamTrans), and Santa Clara Valley Transportation Authority (VTA) through the Peninsula Corridor Joint Powers Board (PCJPB). The system's average mid-weekday ridership is 65,095 as of February 2018.Prior to 2018, Caltrain counted "average weekday ridership" by counting riders on all weekday (Monday through Friday) trains for one week and computing the average as the sum of all riders over one week divided by five. In 2018, Caltrain shifted to counting "average mid-weekday ridership" by counting riders on trains on two of the three mid-weekday days (Tuesday, Wednesday, and/or Thursday) for two weeks and computing the average as the sum of all riders on the four mid-week days divided by four. An examination of mid-weekday ridership data from 2013 through 2017 showed ridership on these three mid-weekday days is approximately equal. Since Monday (-1% compared to mid-weekday ridership) and Friday (-9%) trains tend to have lower ridership than mid-weekday trains, the pre-2018 "average weekday ridership" results in a count approximately 2% less than the 2018+ "average mid-weekday ridership" methodology. Details from 2018 Ridership Report
