Grand Central Terminal Interlocking Charts

It is often quite difficult to find good technical information on New York City region rail infrastructure due to a combination of security theatre and clever employees knowing that information equates to job security.  While some Penn Station information exists on Mark Bej's site, most of what I have on Grand Central is in the form of modern day, paper form track schematics that don't provide much detail and don't provide any historical insight.  For this reason I was quite surprised when an unrelated Google search brought up a result containing not only a complete Grand Central interlocking chart representing the late New York Central era, but also the complete set of locking sheets detailing which levers locked what.

Apparently these diagrams have been around since 2004, so sorry if I am a little late to the party, but if I can miss them I figured they could use a bit more promotion.  The diagrams themselves are in .pdf format so you'll have to click through since I don't feel like making screenshots.  For a quick overview GCT was controlled by 4 interlocking towers, U, A, B and C, each with a GRS Model 2 pistol grip type interlocking machine.  There are another pair of listed interlockings, FA and FB, in service on the loop tracks, but these may have been sections of the A and B machines. Like Buffalo Central Station, the New York Central used a common lever numbering strategy across the entire terminal complex. Lever 1 was in U tower, Lever 1099 was in B tower. This is a good tip to remember if you see photos with lever numbers above 400 and think you've found a contender for the world's largest interlocking machine.

While the diagrams don't have any specific information about the interlocking machines as one might find on an official chart, you can derive much of what you need including frame size and the number of switch and signal levers.  The diagrams also provide one of the best references as to the layout of GCT itself, better than even some of the official documentation which  isn't drawn to scale.  Enjoy!