The subway system consists of close to 25 lines, not including
shuttles. Each line is identified with a number (former IRT
routes) or a letter
(former BMT or IND). The letters toward the beginning of the alphabet
tend to evidence IND heritage, and later ones, BMT. The IND
used a lettering system from its inception, whereas BMT's adoption didn't
happen until after the Chrystie St. connection and related changes took
place in 1967, an event which dramatically changed routings and transit
options. All the
double letter lines of the dimmer past, such as AA and GG, and of the more
recent past such as QT, have
been re-identified or removed.
This station entrance -- constructed obviously in an era long before
consideration for or requirements concerning the disabled -- gives access to
the former BMT's Broadway lines (N, R, Q and W) and the Canarsie Line
(L), as well as the old IRT's Lexington Avenue service (4, 5 and 6).
The system's complexity is pretty awesome.