Most of the New York City Subway was constructed via the cut-and-cover method. That is, a large trench was dug down the center of the street, roadbed, steelwork and concrete work was installed, then the whole works are buried and the overlying streets and utilities are replaced. While other tunneling methods have been used when needed, the cut-and-cover tunnel is what we're focusing on, since it presents the most visual variety.

These rectangular tunnels are supported by roof girders spanning the width of the tunnel on five-foot centers. Vertical girders, in turn support the roof girders at the sides of the tunnel and between adjacent tracks. Generally, the only exceptions to this rule are at crossovers and stations.

You can see in the above photo the five-foot spacing between girders and their accompanying roof supports. Note how the concrete roof is arched between girders.  Within stations, these arches are often flattened out under the mezzazine or wherever a walkway passes overhead (one of these flat spots can be seen on the ceiling just to the left of the foreground "14 St" sign). Walls between stations share this same characteristic. All vertical supports have diagonal bars meeting the roof girder for additional rigidity. Signal cables are bundled together just under these diagonal braces, between the tracks. On the opposite side, above the platform edge and mounted within the diagonal, is a coaxial radio antenna for train crew radios. You'll see the cable running in this area in most of the ceiling shots here.

In stations, the five-foot interval is interrupted over the platform by larger girders spaced at 15-foot intervals holding horizontal girders running the length of the platfom about 3 feet back from the platform edge. The roof girders simply run into, and are fastened to the aforementioned horizontal girder/s. Fluourescent light fixtures run in a string right over the platform edge.

	At Christopher Street, another view illustrates the five-foot spacing between support girders.
	At the north end of 14th street platform, illustrating how the usual 5-foot girder spacing becomes 15 feet beneath the mezzazine level. Included for completeness, you probably won't model this feature if you're modeling a simple single-level station.

Choosing a Station--Index-- Station Signals