at that time, the cars were modified to operate in new arrangements (see letter designations below). In addition, the cars were also modified to allow an entire train's doors to be opened or closed from one point on the train. Prior to this modification, it had been necessary to station a conductor in every car of a train to operate doors prior to the advent of MUDC. Following the modification, one conductor could operate the doors for an entire train. This allowed the BRT, and after 1923, the BMT, to reduce operating costs. The modification involved connecting 9 point jumpers between cars to pass along electric door control signals from the conductor's position. Exterior guard lights had to be added to all cars on all divisions equipped with MUDC (Multiple Unit Door Control). On these cars, these were placed on the same fuse that operated the Empty and Load feature (described below). This was done to save on battery current. In 1927, platforms along the Southern Division stations were being extended to allow for the operation of full length, 8-car trains. Such trains still required the use of two conductors; it was not until September 1958 that they began operating using only one conductor. Further modifications were made in the late 1950s. As the A/B Standards were nearing the end of their useful service life, the New York City Transit Authority set up a plan to retire the cars by the end of the 1960s. Trailers were to be retired first, in the early part of the 1960s. This was a matter of practicality since all trailer cars in the New York City Subway were being phased out. Motor cars would be retired next, starting with the oldest cars (cars 2000–2299, along with a few 2300s). The rest of the fleet would need to serve longer until new car orders could replace them, so cars 2400–2799 were to receive a light overhaul to allow them to serve through the 1960s. Car 2899 was also overhauled, as it was part of a three-car set with two cars (2700s) that fell within the scope of the program. Cars 2800–2898 were not overhauled as they had a non-standard group box switch. The remaining 2300s and the 2800s were retired during the mid-1960s; and the overhauled cars continued in service until the last train operated on August 4, 1969, in Myrtle–Chambers service. Overhauled cars