b4
Bay Ridge Parkway Line Neptune Avenue Line
A 2000 C40LF (988) on the Bay Ridge-bound B4 in Sheepshead Bay. This bus is retired.
Overview
System	MTA Regional Bus Operations
Operator	New York City Transit Authority
Garage	Jackie Gleason Depot Ulmer Park Depot (school trippers)
Vehicle	New Flyer C40LF New Flyer Xcelsior XN40 New Flyer Xcelsior XD40 (school tripper only)
Began service	September 28, 1931
Route
Locale	Brooklyn, New York, U.S.
Communities served	Bath Beach, Dyker Heights, Bensonhurst, Gravesend, West Brighton, Brighton Beach, Manhattan Beach[1], Sheepshead Bay
Start	Bay Ridge – Narrows Avenue and 77th Street
Via	77th/78th Streets, Fourth Avenue, Bay Ridge Parkway, Stillwell Avenue, 86th Street, Shell Road, Avenue Z, Ocean Parkway, Neptune Avenue, Emmons Avenue, Sheepshead Bay Road, Voorhies Avenue, East 14th/East 16th Streets, Ocean Avenue, Shore Parkway, Bragg Street, Knapp Street
End	Sheepshead Bay - Knapp Street and Voorhies Avenue
Length	9.2 miles (14.8 km)
Service
Operates	4:22 AM - 1:20 AM
Annual patronage	1,420,252 (2023)[2]
Transfers	Yes
Timetable	B4
Route map ← B3  {{{system_nav}}}  B6 →

The B4 is a bus route in the New York City borough of Brooklyn, which serves the corridor of Bay Ridge Parkway as well as the majority of Neptune Avenue. Originally operated by the Brooklyn-Manhattan Transit Corporation, it is now operated by MTA Regional Bus Operations under the New York City Transit brand.

The B4 bus route begins at Narrows Avenue and 77th Street, then turns right at 77th Street and continues until turning at 4th Avenue and turning right at Bay Ridge Parkway. It then goes the whole length before running in a zigzag pattern. It turns right on Stilwell Avenue, left on 86th Street right on Shell Road, left on Avenue Z, right on Ocean Parkway, and left on Neptune Avenue. The route continues onto Emmons Avenue then heads left on Sheepshead Bay Road. Between Sheepshead Bay Road and Avenue Z, eastbound buses run via Voorhies Avenue and East 14th Street, while westbound buses run via East 16th Street. On Avenue Z, the B4 runs until Ocean Avenue, where it turns right, then makes a left on Shore Parkway. At Knapp Street, the B4 switches to the opposite direction of Shore Parkway, before making three rights on Bragg Street, Voorhies Avenue, and Knapp Street, respectively. The route ends at Knapp Street and Harkness Avenue. Westbound buses run back to Ocean Avenue via Emmons Avenue, and back to Narrows Avenue via 78th Street.^[3][4]

The B4 is based out of Jackie Gleason Depot, which operates buses that run on compressed natural gas. When school is over at YDE Girls Elementary in Gravesend, Ulmer Park Depot provides trippers from the school to Narrows Avenue, using regular diesel buses. These trippers began in the 2021-2022 school year.

The B4 began on September 28, 1931 under the operation of Brooklyn-Manhattan Transit. Until 1978, the eastern terminus was Stillwell Avenue and 86th Street, with the Emmons Avenue portion served by the B21 bus. It was then extended to Sheepshead Bay with the discontinuation of the B21, giving more Bay Ridge customers a one-seat ride to Coney Island Hospital. On June 27, 2010, the B4 was rerouted from Neptune Avenue to Avenue Z, with off-peak service terminating at Coney Island Avenue due to a budget crisis.^[5] On January 6, 2013, pre-2010 service was restored.^[6]

On December 1, 2022, the MTA released a draft redesign of the Brooklyn bus network. As part of the redesign, the B4 would be straightened in Coney Island, being rerouted to use Stillwell Avenue and Neptune Avenue instead of Shell Road and Avenue Z, replacing the B64 on Stillwell Avenue and having service on more of Neptune Avenue. This would increase reliability by removing turns from the route. Closely spaced stops would be eliminated.^[7]