Facing Point Locks - interlocking & its potrayal in games

[Phil25]

Hello. I'm not really sure where to post this question. Basically I've seen many videos featuring signalmen working at signal boxes but something is confusing me - facing point locks and how they are potrayed in games and how they are associated with mechanical interlocking. I've played many signalling simulations, some of them were more or less realistic. In one game I've played you couldn't reverse a point when FPL was not pulled, when FPL was back to normal the point linked to it was locked. The game later updated and FPLs now are used to release points and you must have them reversed to clear signals. In another game however, FPLs work in the same way as originally in the previous game. Only once FPL is pulled can you reverse a point and you can't clear a signal if FPL is reversed.

One of these games is wrong, but the fact that this differs so much made me wonder how are FPLs actually associated with interlocking. For example, this document I have just found (https://dickthesignals.co.uk/onewebmedia/22 mechanical interlocking.pdf) does not mention that points can be reversed only once an FPL is pulled (I'm even sure how to interpret the locking charts). Could someone clarify this issue?

 

[rower40]

I believe- but could be wrong- that the standard changed during the lifetime of mechanical interlocking.

After all, which is the “safe” state of an FPL?

At the box I worked, the point was free to move when the FPL lever was in the frame, and the lever had to be reversed to clear the signal.

 

[John Webb]

The usual position is the point locked by the FPL when the lever is reversed (ie 'out') in the frame. The FPL lever has to be returned to the normal position to unlock the point and simultaneously lock any relevant signals at 'stop'. There are occasional differences for local reasons.

 

[Annetts key]

BR Western Region practice for normal mechanical points is as follows:

One lever for the point. One lever for the FPL.

With the point in the normal position, the point lever will be in the frame (not pulled) and the FPL lever will also be in the frame (not pulled). This means that the point is locked normal.

To move the points, the signaller has to ensure all levers for all signals reading over the points are in the frame (therefore at danger). then pull the FPL lever to reverse (out from the frame). This "unbolts" (disengages) the FPL.

The signaller can now pull the point lever to move the points to the the reverse position.

Then the signaller normally has to push the FPL lever back in the frame to "bolt" (re-engage) the FPL.

So now, the point lever is reversed, but he FPL lever is in the normal position. Now the signaller can pull the relevant signal lever for that move / route.

This applies in both signal boxes and for ground frames. Occasionally, for moves / routes that are only used for non-passenger train movements, slightly different arrangements may exist.

 

[Phil25]

BR Western Region practice for normal mechanical points is as follows:

One lever for the point. One lever for the FPL.

With the point in the normal position, the point lever will be in the frame (not pulled) and the FPL lever will also be in the frame (not pulled). This means that the point is locked normal.

To move the points, the signaller has to ensure all levers for all signals reading over the points are in the frame (therefore at danger). then pull the FPL lever to reverse (out from the frame). This "unbolts" (disengages) the FPL.

The signaller can now pull the point lever to move the points to the the reverse position.

Then the signaller normally has to push the FPL lever back in the frame to "bolt" (re-engage) the FPL.

So now, the point lever is reversed, but he FPL lever is in the normal position. Now the signaller can pull the relevant signal lever for that move / route.

This applies in both signal boxes and for ground frames. Occasionally, for moves / routes that are only used for non-passenger train movements, slightly different arrangements may exist.

Very interesting, so it's a bit different from other regions. I guess that there is no wrong answer to my question then.

 

[Gloster]

Now I am looking back forty years, but when I worked on both the Western and, before that, the Southern Region, everywhere I worked had the FPL normal when Out. With the lever back in the frame (Normal), i.e. further from the signalman, the point lever could be moved to move the points. Whether the FPL locked the points both Normal or Reverse or both depended on their purpose and could only be done if the point lever was right at the end of the travel, i.e only if the points were right across one way or the other.

Once the FPL was pulled a short way out of the frame the point lever and any other related levers were locked. As the lever was pulled the actual bar at the points moved into its hole in the stretcher bar and so the points were also now physically locked at the point, not just through the interlocking. Now you could pull the appropriate signal and that locked the FPL in place and so the point until the signal lever was put back to Normal (and any relevant track-circuits were clear).

 

[Annetts key]

Please note that I am describing the arrangements for a standard installation of a mechanical point as found on BR Western Region (where I worked for over 35 years regardless of all the name changes).

So, continuing from my earlier post (#4) the point lever controls the rodding to the point via a number of cranks, with the final crank operating a bar whereby it attaches to the first P.Way point stretcher bar (also called the drive stretcher bar). Thus, when you move the point lever, you are directly moving both switch rails of the point. If a crossover, that's four switch rails, two for each point end. This is also the reason that point levers are "heavy" and require more effort to move.

Now, the FPL lever is different. It is not directly involved with the movement of the points at all. Rather, via the rodding run and various cranks, it operates a bar (called a FPL plunger or locking bar) that travels into a cut-out (called a port or slot) in the FPL stretcher bar. Normally there is a port for the normal position and another for the reverse position of the points. The FPL stretcher bar is the large metal bar right at the front (tips of the switch rails), not to be confused with the first P.Way point stretcher bar which is in fact, the second point stretcher bar and is a bit further back.

Before the point can be moved, the FPL lever has to be moved (to the reverse position, out of the frame) to operate the FPL plunger, this lever movement causes the FPL plunger to withdraw out of the port cut into the FPL stretcher bar, thus "unlocking" it and allowing the point switch rails to be moved.

Once the point has been moved, assuming there are no obstructions or other problems that prevent the full movement, the FPL lever has to be moved again. That is moved to the normal position (into the frame), this causes the FPL plunger to travel into the port of the FPL stretcher bar, thus locking it and preventing any movement of the point switch rails.

See the photo below which shows a mechanical point and a mechanical FPL.


Above photo: A facing point lock (FPL) on a set of mechanical points (photo credit: Trevor Bradbeer).

 

[Phil25]

Please note that I am describing the arrangements for a standard installation of a mechanical point as found on BR Western Region (where I worked for over 35 years regardless of all the name changes).

I've found an older thread on this forum also connected to this and it appears to be a more complex topic. People claim that how FPLs work actually depends on local practice and they mentioned some boxes that worked a bit differently. I'm wondering are there any certain areas, other than WR, where FPLs are considered locked when in normal position? Because one the previously mentioned games is 'Blockpost' and people say they make very realistic simulations. For example their Gloucester Road Junction simulation (Southern Region, 1950) seems to have FPLs locked when normal. However when looking at Crow Nest Junction (London Midland, 1958) I can say that FPLs are locked when reversed. I wonder what do people have in mind when choosing the principle.

 

[Annetts key]

I've found an older thread on this forum also connected to this and it appears to be a more complex topic. People claim that how FPLs work actually depends on local practice and they mentioned some boxes that worked a bit differently. I'm wondering are there any certain areas, other than WR, where FPLs are considered locked when in normal position? Because one the previously mentioned games is 'Blockpost' and people say they make very realistic simulations. For example their Gloucester Road Junction simulation (Southern Region, 1950) seems to have FPLs locked when normal. However when looking at Crow Nest Junction (London Midland, 1958) I can say that FPLs are locked when reversed. I wonder what do people have in mind when choosing the principle.

There was no single standard back when signalling evolved, each railway company in the U.K. did it's own thing. Plus there were numerous companies making signalling equipment. So it is perfectly possible that in some places the operation of the FPL lever was opposite to how I described it. That's why I made it clear that I was talking about my experience on Western.

In fact, it would not surprise me if some companies deliberately did things different to their rivals.

And of course, there were other systems if the lever frame operated motor operated points.

 

[AndyPJG]

IIRC in Exeter West SB (at Crewe) the blue FPL levers are reverse to lock the points and free the signal lever.

 

[plugwash]

I can see advantages to both the "default locked" and "default unlocked" approach.

The obvious advantage of default unlocked is that it means that setting up a route is a "simple" matter of pulling levers in the right order. First the points, then the locks, and finally the signal. Whereas with default locked you have to unlock the points, then change them then put the lever back in the frame to lock them again.

The obvious advantage of default locked is it means the points remain locked when not in use and the user doesn't have to touch the "lock" lever when running a train on the "normal" route.

 

[MarkyT]

IIRC in Exeter West SB (at Crewe) the blue FPL levers are reverse to lock the points and free the signal lever.

That's typical for GWR/WR and other frames I've seen. A common example where an FPL stands normally bolted is at a Ground Frame, where the release lever, operated first by crew, also acts as the FPL, withdrawing the bolt as the lever moves from normal to reverse, freeing other levers that move the points. GFs often don't need FPLs, as many sidings have only a trailing point connection into a unidirectional passenger line.

 

[rower40]

Another advantage of “FPL lever normal = Points Free” is this: as already stated, point levers can be a tough pull. The related FPL will often be the adjacent lever. Having it in the frame gives the signaller more elbow room to pull the points over.

The Ground Frame (now converted to signalbox operation) at Bodmin General was as MarkyT describes above. The king lever (released from the box) was the FPL, so was unlocked when reversed. But the other FPLs at Bodmin were (are) unlocked when normal. And there aren’t many boxes further west than Bodmin…

 

[Annetts key]

So in terms of ground frames (GF), here's a photo:

Photo above showing Bristol TM West GF with three levers and an Annetts key lock.
The key is obtained from the instrument (not shown) when the signaller gives "a release". It is then inserted into the lock (painted blue to the front left of the levers between the wood deck and the rail in the foreground). When turned, this unlocks the frame.
Now the FPL lever can be pulled (painted blue). Then the point lever (painted black) can be moved). If a FPL is required for the reverse position, the FPL lever must be put back. Then the red slot lever can be pulled to allow the relevant signal to be cleared.
Some GF also have an electric lever lock for some levers, in which case a push to press plunger switch must be operated before you try to pull the lever.

And here's Bristol TM East GF which is similar:

 

[Belperpete]

There were cases where the same FPL lever locked one set of points when normal, and a different set of points when reverse. As say up direction signals would need the FPL lever normal, and down direction signals would need the FPL lever reverse, this saved having to provide locking directly between the signal levers.

== Doublepost prevention - post automatically merged: 3 Oct 2025 ==

BR Western Region practice for normal mechanical points is as follows:

Having worked on BR Western Region too, I am a bit wary about stating that something is "WR practice". A couple of times I found that what I have been told is "WR practice" actually turns out to be "WR xxxx Division practice", and another WR Division did something different. My experience was as per Glocester and MarkyT, that for WR signalboxes the FPL lever was pulled to lock the points. Only with ground-frames are the points locked by the FPL lever normal.

As for the Southern, I have a copy of the SR "Brown Book" on locking, which states that "All bolt locks operated by separate levers to lie normally out when the lever is back in the frame." In other words, you have to pull the FPL lever to lock the points. However, this would have been applied to new work. They wouldn't have made retrospective changes to existing signalboxes unless doing a major relock.

My understanding is as per rower in post #2, that early signalboxes had FPLs that worked the same as those in ground-frames, i.e. points normally locked, but at some time signalbox practice changed to points normally unlocked. I have a suspicion that, because this seems to have happened on more than one railway, this change could have been influenced by HMRI.

 

[Annetts key]

There were cases where the same FPL lever locked one set of points when normal, and a different set of points when reverse. As say up direction signals would need the FPL lever normal, and down direction signals would need the FPL lever reverse, this saved having to provide locking directly between the signal levers.

== Doublepost prevention - post automatically merged: 3 Oct 2025 ==


Having worked on BR Western Region too, I am a bit wary about stating that something is "WR practice". A couple of times I found that what I have been told is "WR practice" actually turns out to be "WR xxxx Division practice", and another WR Division did something different. My experience was as per Glocester and MarkyT, that for WR signalboxes the FPL lever was pulled to lock the points. Only with ground-frames are the points locked by the FPL lever normal.

As for the Southern, I have a copy of the SR "Brown Book" on locking, which states that "All bolt locks operated by separate levers to lie normally out when the lever is back in the frame." In other words, you have to pull the FPL lever to lock the points. However, this would have been applied to new work. They wouldn't have made retrospective changes to existing signalboxes unless doing a major relock.

My understanding is as per rower in post #2, that early signalboxes had FPLs that worked the same as those in ground-frames, i.e. points normally locked, but at some time signalbox practice changed to points normally unlocked. I have a suspicion that, because this seems to have happened on more than one railway, this change could have been influenced by HMRI.

Yeah, apologies, I think my memory was playing tricks on me. I now think it's likely either there were different standards in use at different times (the railways in Britain are good at that) and because mechanical locking frames only get changed when they absolutely have to, retrospective non-safety critical changes are either not done or it takes many, many years before the alteration is made. Or there was no standard and it depended on other factors.

Oh, and it's not helped by some signal boxes having been rebuild due to damage during WWII and some former Midland signal boxes having been transferred to Western...

 

[Tester]

An interesting summary, which takes me back a bit!

In short, both methods of working are functional and established - therefore both simulations are valid.

Welcome to the wonderful world of British Railway Signalling!

 

[Ashley Hill]

From my experience on western frames FPLs on signal box frames stand out to lock ie lever reverse. On GFs as shown at Bristol above FPLs stand in to lock ie lever normal.

 

[Gloster]

I may be getting mixed up with something else, but having FPL levers Normal when In in ground frames was to avoid having one lever sticking out and at risk of having someone fall over it: a full row of levers in a ground frame is more visible. In signalboxes having the FPL levers Reversed when In can provide a quick check for the signalman.