, over 5,710 MTA Regional Bus Operations-operated buses carried about 2.5 million daily passengers 24/7 on more than 238 local routes, 62 express routes, and 7 Select Bus Service routes, amounting to 793 million annual bus trips. Buses owned by MTA account for 80% of the city's surface mass transit. New York City has the largest clean-air diesel-hybrid and compressed natural gas bus fleet in the United States. Local bus routes are labeled with a number and a prefix identifying the primary borough (B for Brooklyn, Bx for the Bronx, M for Manhattan, Q for Queens, and S for Staten Island). Express bus routes operated under MTA New York City Bus use the letter X rather than a borough label. Express bus routes operated under MTA Bus (formerly controlled by the NYC Department of Transportation) use a two-borough system with an M at the end (i.e., BM, BxM, SIM, or QM). Additionally, MTA offers precise bus arrival time using QR code located at each stop. Some stops also have digital panels indicating arrival times.