from 1968 to 1976, when F trains ran express in both directions between Bergen Street and Church Avenue during rush hours. G trains were extended from Smith–Ninth Streets to Church Avenue to provide local service. Express service between Bergen and Church ended in 1976 due to budgetary concerns and passenger complaints, and the GG, later renamed the G, was again terminated at the Smith–Ninth Streets station. In July 2009, the G was extended from its long-time terminus at Smith–Ninth Streets to a more efficient terminus at Church Avenue to accommodate the rehabilitation of the Culver Viaduct. The G extension was made permanent in July 2012. In July 2019, the MTA revealed plans to restore express service on the Culver Line between Jay Street and Church Avenue. Express service started on September 16, 2019. Station layout This underground station has two tracks and an island platform. The two express tracks of the line run along a more direct alignment under Prospect Park, and are not visible from this station. The station is approximately long and wide, excluding exits and passageways. The station and tunnel were constructed about east of Prospect Park West. Therefore, the station is not located underneath a street. Some portions of the tunnel are directly underneath Prospect Park, while others are between Prospect Park West and 10th Avenue. Both trackside walls have an orange-yellow trim line with a medium red-brown border with small black and white "15TH ST" tile captions below it at regular intervals. The tile band is set in a three-high course, a pattern usually reserved for express stations. The tile color was part of a color-coded tile system for the entire Independent Subway System. Ventilation grates are located along the trackside walls. A row of large, white tiled columns runs along either side of the platform and the mezzanine above at intervals. Alternating columns carry the standard black-and-white station name plate. The ceiling of the platform level is held up by H-shaped piers located every , which support girders underneath the mezzanine. The roof girders are also connected to columns in the trackside walls. The tunnel is covered by a "U"-shaped trough that contains utility pipes and wires. The outer walls of this trough are composed of columns, spaced approximately every with concrete infill between them. There is a gap between the tunnel wall and the trackside wall, which is made of -thick brick covered