Interlocking System

The to-and-fro movement of a dense traffic on a four-track railway requires a large amount of switching, especially when each movement is complicated by junctions of two or more lines. Practically every problem of trunk line train movement, including two, three, and four-track operation, had to be provided for in the switching plants of the subway. Further, the problem was complicated by the restricted clearances and vision attendant upon tunnel construction. It was estimated that the utmost flexibility of operation should be provided for, and also that every movement be certain, quick, and safe.

All of the above, which are referred to in the briefest terms only, demanded that all switching movements should be made through the medium of power-operated interlocking plants. These plants in the subway portions of the line are in all cases electro-pneumatic, while in the elevated portions of the line mechanical interlocking has been, in some cases, provided.

A list of the separate plants installed will be interesting, and is given below:

Location.Interlocking
Machines.		 Working
Levers.
MAIN LINE.
City Hall,332
Spring Street,210
14th Street,216
18th Street,14
42d Street,215
72d Street215
96th Street219
WEST SIDE BRANCH.
100th Street,16
103d Street,16
110th Street,212
116th Street,212
Manhattan Viaduct,112
137th Street,217
145th Street,219
Dyckman Street,112
216th Street,114
EAST SIDE BRANCH.
135th Street,26
Lenox Junction,17
145th Street,19
Lenox Avenue Yard,135
Third and Westchester Avenue Junction,113
St. Anna Avenue,124
Freeman Street,112
176th Street,266
————
Total,37393
The total number of signals, both block and interlocking, is as follows:
Home signals,354
Dwarf signals,150
Distant signals,187
——
Total,691
Total number of switches,224

It will be noted that in the case of the City Hall Station three separate plants are required, all of considerable size, and intended for constant use for a multiplicity of movements. It is, perhaps, unnecessary to state that all the mechanism of these important interlocking plants is of the most substantial character and provided with all the necessary safety appliances and means for rapidly setting up the various combinations. The interlocking machines are housed in steel concrete "towers," so that the operators may be properly protected and isolated in the performance of their duties.