Diamond services

Normal and diamond 7 bullets

Despite its efforts toward single identifiers for each service, the MTA has adopted a variation of a signage practice that began with street railways, in which a variant service is identified with a special color or symbol on the route number signs. This has been implemented on the subway by use of diamond services. Since a route letter or number is ordinarily presented inside a circle, variants of the same service are shown as the same letter or number inside a diamond shape.

Special services

An R46 LCD sign on the IND Sixth Avenue Line

Special is a signifier for a train that is running along a nonstandard route. It is sometimes used for special holiday trains,^[7][8] baseball game service,^[9] or for emergency or custom routes. Most trains have a "Special" option on the rollsigns or LCD/LED displays.^[10]

BMT/IND service label integration

When all three systems came under city ownership in 1940, essentially nothing was done to standardize signage for two decades. Stations on the IRT and BMT still said Interborough or BMT Lines or sometimes older designations. Services continued to be signed by their traditional methods for each system. IND and post-Second World War ("R-type") equipment used BMT numbers when operating on BMT services. With the introduction of R12 equipment on the IRT in 1948, IRT subway services (except for the 42nd Street Shuttle) began using the route numbers still used today, which had been used internally but not on trains or maps. Astoria Line trains were only signed as 8 for a year, after which the line, which had been shared with the BMT, was converted for BMT operation only (and the Flushing Line carried only IRT trains).

In 1960, with the delivery of the first R27 class cars for the BMT, the New York City Transit Authority (TA), which had become the operator of the combined system in 1953, began the introduction of letters for BMT services in anticipation of integrating the BMT and IND operationally. The last IND letter used was H, and the letter I was skipped as being too similar to the number 1. The BMT Eastern Division services got the letters J, K, L and M. The BMT Southern Division services were designated N, Q, R and T. P was for some reason skipped over, and while one theory says this was because it might lend itself to bathroom humor, the letter's undesirability for this reason would seem to be disproven by the fact that the letter was later proposed for an emergency line that would replace Long Island Rail Road service to Penn Station in the event of a strike, and the fact that other cities like San Francisco use the letter. A more likely theory suggests that it was originally planned for the last segment of Culver service to Manhattan, which was cut back to a shuttle permanently in 1959, right before the letters were introduced. S was still reserved for "Special" and SS began to be used for shuttles.

Since the BMT was not amenable to the neat IND system, the TA had to make some compromises. They tried to follow the IND system of single-letter expresses and double-letter locals, but the system began to break down under the complex BMT routings. Where on the IND a local simply doubled the express letter (A Eighth Avenue Express, AA Eighth Avenue Local), some lines had multiple local services with different routings. For instance the two Brighton Local services, one via the Manhattan Bridge and the other via the Montague Street Tunnel, were designated QB and QT respectively. The TA had no specific lettering plan for the two Wall Street special rush-hour services, so it just designated these M (Nassau Street Express) temporarily, a letter reserved for use on the BMT Myrtle Avenue Line's Nassau Street service.

During this period, the TA did not change sign rolls on BMT equipment (the D-types and R16s) that carried numbers, so that on the Brighton Line, the R27-operated locals were signed QB or QT but the D-type-operated expresses continued to carry the number 1.

Chrystie Street Connection

A typical post-1967 side rollsign

In anticipation of the 1967 opening of the Chrystie Street Connection, which combined two major BMT and IND services as single routes and resulted in numerous other changes (especially on the 14 and 15), the TA decided to adopt universal systems of signage and nomenclature. The rationale was that this would make the system more consistent and more understandable for newcomers to the city and tourists, who were presumed to be uninterested in or even confused by historic or community names, or might not be native English speakers.

• Branch line names would be eliminated from signage and maps; all services that had Manhattan mainlines would be identified by those names only.
• Services would be identified only by letters or numbers wherever possible, even when announcing reroutings.
• Terminals would be identified by street names rather than community names where that existed. This had actually begun with the introduction of R-type equipment, when destinations such as Woodlawn and Canarsie were changed to read Woodlawn Road (which is no longer the name of a road) and Rockaway Parkway.
• All services would be color-coded for map and rollsign purposes. This proved a daunting task, since the TA wanted to ensure that no two services with exactly the same color would operate over the same line. With a lot of imagination and a lot of color variations, this goal was achieved but proved unwieldy. The colors did not have any particular logic and still produced ambiguity; notably the A service and the E service shared miles of line between Midtown Manhattan and the Rockaway Line in Queens, one as an express, the other as a local. But the A was colored dark blue and the E light blue, not always easily distinguishable.

The 8 designation was brought back for the only remaining IRT elevated service, the IRT Third Avenue Line in the Bronx but trains never displayed the number. When the Lo-V cars (which did not have front signs) were replaced by R12 cars the front roll signs in use did not contain the number 8 and instead displayed the word shuttle. For map and sign purposes MJ was assigned to the last old-style elevated line, standing for "Myrtle Avenue Line to Jay Street", while the "Myrtle Avenue line to Chambers St." subway service would finally receive its M designation. The short-lived new Sea Beach Line super-express service was made NX. The Q, QT and T disappeared when the Chrystie Street Connection opened; thus they never had colors (until after the elimination of double letters, when the Q came back; by that time the current color system was in place). By 1968, all shuttles (SS) were green. For a short time, the off-hour shuttle between Metropolitan Avenue and Myrtle Avenue was added in 1969 when the MJ service to Jay St. was discontinued, and that part of the line abandoned. The shuttle was soon renamed "M", however, as it only ran when the M did not run to Manhattan.

The system immediately showed evidence of problems for various reasons:

• Different services at common stations shared common destinations by different routes. N, B and QJ services arriving at DeKalb Avenue, for example, all had Coney Island as a destination, but had no mention of the widely separated routes (Sea Beach Line, West End Line, Brighton Line) used to get there.
• Service labels are ephemeral. The TA has frequently shifted lettered routes from one branch line to another, and introduced, changed or deleted letters, making a description like "the D train" meaningless. The D service has been on three completely different Brooklyn branch lines since 1954. K was introduced for a service on the Broadway-Brooklyn Line but was later used for the IND Eighth Avenue Line local which had formerly been AA.
• The same lettered or numbered lines may have different destinations by time of day, despite a largely successful effort to minimize this problem.

Elimination of double letters

This brochure was published in 1985 to explain the relabeling of double-letter subway services

On June 25, 1979, the former color scheme was scrapped, and the TA settled on the more coherent policy of assigning the same color to every service on each Manhattan mainline, as well as the color lime green for the IND Crosstown Line, which does not enter Manhattan. The same colors are still used today. Nevertheless, no New York subway line is officially referred to by its color, e.g., BMT Broadway Line services as the "Yellow Line." While referring to lines by their color, as is common in some other cities, is a convenient shorthand for the regions of Manhattan where lines and colors are relatively unambiguous (from roughly Houston Street to 50th Street, and further uptown for the "red" and "green" lines), this practice would be confusing outside of that region (due to multiple services being assigned the same color).

On May 5, 1985, the last significant change in route identification policy was made after the TA had decided in 1981 that the single and double letter system of the original IND was no longer meaningful, given that there were many services that were express for part of their route and local for other parts. In most cases, this was accomplished by simply eliminating the second letter in route designations. There is no longer a letter designation for specials (formerly S).

By the 1990s, the TA were moving steadily toward using traditional line names on maps and especially on signage. All of the southern Brooklyn subway lines now show the traditional line names (except for the BMT Fourth Avenue Line) in order to distinguish between services going to Coney Island via different lines. On BMT/IND equipment, branch line names frequently appear on operating trains, in addition to the route letter. R32 equipment with rollsigns, for example, may read:

207 Street Manhattan Mott Av Far Rockaway Wash Hts/8 Av/Fulton

Ditmars Blvd Astoria Stillwell Av Coney Island Astoria/Bway/Sea Beach

57 St–7 Av Manhattan Stillwell Av Coney Island Broadway/Brighton

Newer rollsigns on R40 up to the R68A (including the former rollsigns on the R44 and R46 that now have LCD displays) have the route's bullet on the left side, and the two destinations on the right side. A rollsign on an R68 D train may read:

	Norwood, Bronx 205 St
	Coney Island

One change which precedes pre-unification has to do with the use of locality names. While these were discouraged during the 1960s after they had been inherited from private operators, many terminal stations are once again described by both a community and a street name; e.g., Inwood–207th Street for the northern destination of the A service, and Wakefield–241st Street for the northern destination of the 2 service.

An R142 side sign indicating that this 4 train runs express on the IRT Eastern Parkway Line

The same sign shown in animation

The JFK Express, started in 1978 and discontinued in 1990, used a turquoise bullet; this stayed through the color change.

Route consistency

Since the unsuccessful attempts at applying the briefly popular schematic theory of diagrammatic maps, line-by-line color-coding, and exclusive use of numbers and letters for service and line descriptions, the MTA has moved steadily toward a more traditional approach, with more geographically correct maps and use of traditional line and community names on maps and public signage. Concurrently, it has been refining its use of the number and letter system to try to achieve consistency across the system.

One major push has been an attempt to have as many services as possible serve the same stations, routes and terminals at all times, with the major exception for most services being the early morning hours of approximately midnight to 5 a.m. For instance, the B and C swapped northern terminals in 1998 so the C could serve the entire local portion of the IND Eighth Avenue Line at all times except nights; previously, the A had made two local stops north of 145th Street on weekends, while being express on the whole line south of 145th Street, because the B did not operate in Manhattan on weekends. In another case, the MTA took advantage of unavoidable service changes forced by the partial Manhattan Bridge closures to swap the Brooklyn segments of the B and D services, with the B becoming the BMT Brighton Line express service and the D becoming the BMT West End Line local (previously the B had been the West End Local and the D the Brighton Local). This enabled the D, a full-time service, to operate continuously on the same route and terminals from Norwood–205th Street in the Bronx to Coney Island–Stillwell Avenue in Brooklyn, while the part-time B became the part-time Brighton Express service, formerly served by the express <Q> (notated with a diamond).