The Brighton Line's single island platform for the two tracked line at Atlantic Avenue are by far the deepest of any in the station, this is probably because they must cross underneath the LIRR Station before joining the IRT for a shared six-tracked ROW underneath Flatbush Avenue. The platform is a rare BMT station that was built with a full (but quite narrow) IND-style upper mezzanine, unforchunately the mezzanine has been cut into 3 different sections, with just small areas by each platform exit still open to the public, and the areas in between the exits used as an office and shop for Maintenance of Way. The platform itself has columns along it that are mostly tiled except for some towards its ends that are bare I-beams painted blue. Most of these columns have Atlantic Avenue signs along them. The platform walls were all retiled over during a 2004 renovation and have a standard carefully mosaiced dual-contracts trim-line at their tops, with A's in it at regular intervals. There are also Atlantic Ave name tablets at regular intervals along the platform walls. In 2004 there was an older black text on white platform sign but this has been removed/covered over for standard black with white text signs.
The staircases and elevator that lead to the long mezzanine artery to connect to the other subway lines at the Atlantic Avenue complex are station are towards the middle of the platform. This leads up directly to two small fare control areas (all with high exit turnstils) on each side that provide access to LIRR tracks 1 and 2. There is an additional exit only (as the signs say) exit towards the northern (western) end of the platforms. Two staircases lead up from the platform where a longer staircase, as well as an up escalator (the distance is definitely long enough to warrant an escalator) lead to a small upper mezzanine area where automated fare control is (High Entrance/Exit Turnstiles), and an exit that is at street level within the Williamsburg Savings Bank Building, 1 Hanson Place, the tallest building in Brooklyn. There is another staircase from this landing (closed due to construction when I first visited) leading down to the main LIRR underground atrium.
September 17, 2012 Update: Today a new entrance opened at the now renamed Atlantic Avenue-Barclays Center Station Opened: There are two staircases at almost the eastern (Coney Island-bound) end of the platforms that lead up a small upper landing with a short passageway that leads up passed a few double doors to another staircase before arriving at the new Barclays Center entrance alongside ramps that provide a new, much less crowded connection to IRT 2,3,4 and 5 trains.
Photos 1-6: June 18, 2009; 7-13: June 29, 2009; 14-18: February 3, 2004; 19 & 20: December 28, 2010; 21-26: September 17, 2012; 27-30: November 1, 2012; 31: December 14, 2012
Station Subway Lines (2000-2004)