In the third quarter, U.S. transit ridership slipped 3.65 percent year over year to 2.503 billion total trips.

Nine of the 10 largest transit agencies in the nation reported declines for the quarter. Some agencies attributed the downtick to an increase in auto travel and continued low gas prices, according to the American Public Transportation Association‘s (APTA) Passenger Transport newsletter.

“Even if a small number of public transit riders choose instead to drive, they may have an outsized effect on the change in ridership as measured in unlinked trips,” the newsletter stated.

By transit mode, heavy-rail ridership in the third-quarter fell 3.05 percent to 938,699 trips compared with the same period a year ago, while commuter-rail ridership declined 1.33 percent to 125,249 trips. Light-rail ridership fell 1.9 percent to 138,170 trips, and overall bus ridership decreased nearly 5 percent to 1,168,888 trips.