Interlocking Walkthrough: F

For this week's interlocking Walkthrough we'll take a brief step out to Queens for some fresh air as we take a look at F interlocking.  F interlocking is the interlocking eastbound trains first come to right when they exit the East River Tunnels.  While it is not as complex and vital as HAROLD interlocking, it's neighbor immediately to the east, F interlocking does play a key role for trains going to or coming from Sunnyside Yard.

To start off, here is a diagram of F interlocking.  Now as a word of caution: there's a lot of exciting and interesting things in this interlocking, and they will all be explained in due time, but it might take a week or two as we are still embroiled in the Penn Station mess:

The main purpose of F interlocking is to take trains that are coming out of the East River Tunnels and send them off to, or take them from, the various lead tracks to Sunnyside Yard.  Since the LIRR does not use Sunnyside Yard, there aren't too many occasions a LIRR train would venture down the lead tracks, but they are important nonetheless.

A NJTransit equipment train headed for Sunnyside
Yard (Photo credit: The LIRR Today on Flickr)

Sunnyside Yard is a major storage yard and maintenance facility for Amtrak and NJTransit trains.  There are more than 30 tracks for train storage as well as various other facilities that allow Amtrak to service its trains there.  The yard tracks themselves lie directly to the north of the main tracks here and they have an interesting way of tying into the East River Tunnels.

Since the tracks in Queens are sorted by direction (a concept we'll get into next week), Sunnyside Yard is capable of functioning as a giant loop.  Trains can come out of the eastbound lines, go onto the yard leads, loop around and pass through the yard, come out on the exit leads and get back into the westbound lines without causing one bit of trouble.

Because of the loop (trains are essentially looped on their way in), turning trains is made substantially easier.  Trains could essentially run through the yard without stopping and the engineer would not have to change positions, walk the train, or anything.  Furthermore, for Amtrak trains, which frequently only operate with a leading locomotive, it saves yard crews the trouble of physically wying or trying to find some way to turn a train.  It comes into the yard looped already.

F interlocking is where these yard leads  rejoin the main tracks.  The entrance leads split off the eastbound (outbound) tracks and the exit leads merge into the westbound (inbound) tracks.  And since the Pennsylvania Rail Road loved little more than flyovers, there are a number of overpasses and underpasses that allow all of this to take place without conflicting train movements.

NJtransit trains lurking on the Sunynside Yard exit leads.
(Photo credit: The LIRR Today on Flickr)

The eastbound lines (lines 1 and 3) allow for easy access to the entrance lead tracks and the westbound lines (lines 2 and 4) allow for easy access from the exit lead tracks.  This makes maintaining a continuous current of flow very easy to do, since you can have multiple trains moving around this turning loop at any time.  This setup, however, also makes it very difficult to go against the grain.  If you intend to come out of the East River Tunnels going in the wrong direction you will only be able to access either the entrance of the exit leads.  So if a train comes out of Line 4, the only way it can get into Sunnyside Yard is to sneak in on the exit leads, since there is no physical way for a train to get all the way over to the other side of the interlocking.   Since tunnel outages and the like can make situations like this necessary, there is no specific rule preventing someone going the wrong way around the loop.  But for daily operations where there is hundreds of movements into and out of the yard daily it does help substantially to have everything moving in one direction.

Old position light signals standing in front of new
tri-color light signals that were installed years ago
(yet they are still OOS and bagged...)
(Photo credit: The LIRR Today on Flickr)

Other than the Sunnyside Yard leads there are also a bunch of other miscellaneous switches  tossed in.  In particular, there are a couple of switches that connect the LIRR Main Line (coming from Hunterspoint Avenue) to the rest of the tracks in HAROLD interlocking.  Also, the Main Line Cutoff (the what!?) drops down in the middle of F interlocking too.

F interlocking is currently undergoing transformations (as is everything else around this area), and a number of improvements, such as the replacement of the old position light signals with tri-color lights is underway, but slow going.  In particular, they installed a number of new signals around Hunterspoint Avenue ages ago, yet they are still bagged up and out of service.  Maybe they'll get around to turning them one one day...  But, until then, we'll continue with our tour of Penn Station's platforms and tracks tomorrow, before we move onto even more crazy things.  Stay tuned!