Interlocking Walkthrough: HALL

Today, we're going to be taking a look at one of the LIRR's biggest interlockings- HALL interlocking. HALL Interlocking can only be competed by it's sister interlocking, JAY interlocking, which controls the part of Jamaica where trains are coming from in the west, therefore, complementary to it, this interlocking controls trains coming into Jamaica station from points east.

While I like to say all 3 Jamaica interlockings- HALL, DUNTON, and JAY are important, I like to think that JAY and HALL are the more important ones, as they are busier, and as DUNTON is also off to the side a bit only controlling a much lesser portion of trains on the Atlantic Branch. The busier JAY interlocking will be featured in a post in a couple of weeks.

HALL Interlocking is so large that I think it's almost impossible to explain it and it would be quite a long post if I attempted to, therefore, I'm going to try my best to sum it up and explain it from there. I'll give you the "gist", and once you get the "gist", you should be able to figure out the rest of the interlocking from there. 

However, thanks to a very handy-dandy NYC subway trackmap, you'll be able to see what HALL looks like in detail:

As you can see, HALL's borders extend from where the Babylon Branch (uhm, excuse me, Montauk Branch) join in to the last switch before Jamaica station begins going westbound.

While I think that diagram makes this interlocking look much simpler, I still believe it can be very confusing to grasp, at least at first.

You'll notice how the tracks of both the Atlantic Branch (shown below), and the Montauk Branch have to try to get off of HALL interlocking so they can head towards the South Shore, therefore, they duck under the interlocking in order to get away from it. 

Here's another photo that more clearly shows it:

You'll notice that the same thing happens a bit later on into the interlocking with the Montauk Branch heading off, however, when it's their time to leave the Main Line, they rise all the way up and go over the eastbound tracks, oppose to under like is seen with the Atlantic Branch. 

Now, go into Google Earth and take a look at the interlocking, and also note that the Atlantic Branch tracks leave from the middle, however, you'll notice that the Montauk Branch tracks leave from the center, too. All of this was done specifcally with the intent of streamlining the interlocking, allowing eastbound and westbounds to stay apart from each other the entire way, in this way, this allows the LIRR to operate this massive amount of trains through the interlocking.

In addition, with the way it was separated, a dispatcher wouldn't have to wait for an eastbound Montauk Branch train to go before a westbound Main Line train could go, even further simplifying operations. I feel that the way they made this interlocking made it geniously-designed to handle all the immense train-traffic it has to manage, the way they had the 2 branches leave the Main Line without disrupting the flow of the other Main Line traffic is just genius and probably took a lot of work to get right.

I tried to simply this interlocking walkthrough, considering the immense complexity of the actual interlocking, and if it doesn't make sense, trust me, once you read the JAM interlocking walkthrough, when it comes out, it'll all come together. Trust.