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Marylebone - LUL Signaller Area

Introduction

In real life the LUL section is covered by multiple signallers using a mixture of miniature lever frame signalboxes and push-button panel signalboxes. In SimSig we have the advantage of entrance-exit VDU-based routesetting, also with Automatic Routesetting, so we don't need so many signallers.

There are two versions of the LUL section, selectable upon startup. The simple version consists of basic 3-aspect signalling throughout the entire LUL section without sidings or junctions and does not require user intervention. No LUL trains will run in this instance. The detailed version contains the LUL track layouts and signalling with automatic routesetting. The latter of these is described below. Note that LUL trains are categorised as 'Other' in the F3 ARS menu .

A Brief Summary of LUL Metropolitan Line Signalling

The following is intended as a brief introduction to the signalling as used in this section of London Underground's Metropolitan Line between Harrow-on-the-Hill and Amersham. What happens here is not necessarily representative of LUL as a whole.

3- and 4-Aspect Signalling on the Main Lines

North of Harrow, the Main lines employ 3- and 4-aspect signalling which is almost indistinguishable from Network Rail signalling of the same type.

Auto Signals

Automatic signals are identified by an "A" prefix - for example, A771 on the southbound local at Northwood Hills. This particular signal is a two-aspect signal capable of displaying red or green aspects only.

Sometimes the signals are suffixed A or B. Taking the northbound local at Moor Park as an example, the platform starter (JJX790) is preceded by signal A788B which is itself preceded by A788A. If JJX790 is at red then both A788A and A788B will also be at red. Each of these (A788A/A788B) in turn will show green once a train approaches and is timed to nearly a stand. This brings the train closer to the train in front whilst controlling its speed for safety.

Thus the sequence with JJX790 at red is:

- A788A and A788B are at red

- Train approaches A788A: signal shows green when train is nearly at a stand at that signal

- A788B is still red

- Train passes A788A: this signal now returns to red

- Train approaches A788B: signal shows green when train is nearly at a stand at that signal

- Train is now approaching JJX790 at a much reduced speed, preparing to stop.

Controlled Signals

In LUL terms these are semi-automatic signals. These are identified by not having an R or A prefix. In SimSig routes can be set in the usual way.

Note that many controlled signals with a single route will set with just a left-click on the entrance signal (one button control). This simulates the single lever control available to real life LUL signallers.

Repeater Signals

These are identified with an R prefix. A single controlled or automatic signal may be preceded by zero, one, or many repeater signals in order to give enough sighting distance for a train to stop at such a controlled or automatic signal.

Signal A767 between Northwood Hills and Pinner on the Southbound local has two such repeater signals for that signal.

Auto or Controlled Signals With Attached Repeaters

Sometimes the distance between a controlled or automatic signal and the next controlled or automatic signal is insufficient for trains to stop. In such cases, the signal also has a repeater signal underneath the main signal. If one were to ignore the physical features of the signal and only see the lamps in the dark, the possible aspects would be:

- Red: Stop

- Green over yellow: Proceed, prepared to stop at the next signal

- Green over green: Proceed, with next signal displaying a proceed aspect

Display

Because the LUL area is controlled with miniature lever frames and panels with simple occupancy lights, it is sometimes too simple to display on SimSig which likes to be accurate about what it portrays. Thus what you see is a compromise between a signalling display system designed for British main line railways and a control system designed for London Underground signalling systems.

The first oddity to note is that overlaps are usually only illuminated where they pass over pointwork. This is because they often extend only part way into a displayed track circuit, and would result in more confusing displays if they were to be shown. Consequently, overlap markers are also not shown for simplicity. Finally, there are short and long overlaps in certain areas, selected by "Normal" or "Leaf Fall" options where, in the latter case, overlaps are extended to account for slippery rails.

Spring points exist in four locations at Harrow. These points cannot be worked manually and are operated by trains passing over them in the trailing direction. Consequently, any routes through such points show the entire point rather than the position that would be shown for a controlled point. Spring points are denoted by a $ symbol.

Generally, routes on plain line will not show up with white track lights. Only the signal post will show that a route is set (being in white instead of grey).

Train Describer

In real life, LUL doesn't use a train describer in the form that the national rail network does. LUL use a system called Train Tracker which probably tracks trains on a track circuit basis, more akin to foreign practice than the UK.

In SimSig we have a representation of a train describer had they used one in this area. Not every signal has its own TD berth; only each signal block section. Thus trains won't be "lost" but it may appear that a train is at a signal without a TD.

Also note that LUL use three-digit train IDs whereas SimSig (and train describers) use four-character IDs. Thus timetables need a prefix on the train ID to bring it up to four characters. This is usually a letter on the front, so train 123 becomes A123 (or whatever letter is appropriate).

Because of the way the track layout is arranged, TDs may step before the next visible track becomes occupied. This is because each track is often made up of two or more part tracks. The TD steps when the part track beyond the signal becomes occupied but visually there is no difference to track occupancy on screen, but the TD has stepped anyway. But this will coincide with the signal returning to red which gives a clue that the train has passed the signal and is now entering the next section.

Locations

Mantles Wood

The location identified as "Mantles Wood" is the official boundary between LUL and Network Rail territory, between Amersham and Great Missenden. Apparently this is not the exact location, but then the railway is not exactly known for being geographically perfect - more geographically convenient. Still, the boundary has a name but a discussion of what it ought to be called can be found here and there's even a photo of one side of the boundary

here .

Amersham

The northern extent of the Metropolitan Line. Trains used to run all the way to Aylesbury and even beyond in the past, but Amersham is now the northern terminus. All three platforms can be used to turn back towards London, though platform 1 ought to be kept clear for non-stop main line trains to Aylesbury as that is the faster route.

Two sidings to the north of the station can each hold a single LUL train. A further siding to the south, 34, is not electrified and thus cannot take a standard LUL train. Diesel main line trains (or battery/diesel underground trains) may use it.

Chesham

A single track branch extends from Chalfont & Latimer to Chesham. This winds its way through the countryside for a few miles before ending on the edge of the town of the same name. Previously Chesham had more platforms but nowadays just the single platform remains. As there is no pointwork, or signalling, most of the branch consists of a single Axle Counter section. Note that trains going to Chesham and back will occupy the axle counter section for at least a quarter of an hour.

Chalfont & Latimer

A short bay holds a half LUL set, as used for the Chesham shuttle at various times. Full size sets have to use the through platforms.

The section from here to Rickmansworth travels through wooded sections and is liable to have slippery rails in leaf fall season. There is a speed restriction through the area when this is in effect and some signals have longer overlaps, both to attempt to mitigate against overrunning trains.

Chorleywood

This through station used to have its own signalbox until not so long ago. Nowadays it's a station in the middle of auto signalling sections.

Rickmansworth

Eight sidings around the station provide berthing facilities for trains during the day and overnight. Each siding can hold one LUL set, with the exception of number 23 which can hold a double unit. Each siding has a single TD berth, again except for number 23 which has two TD berths.

Trains arriving from the south and terminating at Rickmansworth may use either platform 1 or platform 2. Be careful not to end up with two trains facing each other through platform 2.

Sidings 31 to 35 do not have signals in real life. The LUL signaller talks to the driver and gives verbal authority via lineside speakers and microphones, both for movements into the sidings, and movements out of the sidings. However, the points are power-operated from the signalbox. In SimSig we can set routes into and out of the sidings in the usual entrance-exit style.

Watford

Two platforms and three sidings are provided here. Note that number 24 siding extends from the buffer stops out to signal JP125. For timetabling purposes the siding has two identities: use Watford (station), platform 24 for the station end, and location "Watford No.24 Road" for the London end.

Inbound trains from Croxley cannot be signalled to signal JP134 until either:

• Siding 21 is completely empty AND route is set from JP134 into the siding
• Platform 1's country end track circuit is clear
• Platform 2's country end track circuit is clear
• Siding 24's country end track circuit is clear AND route is set from JP134 into the siding

Trains reversing via signal JP118 may need their TD interposing at signal JP118 otherwise ARS may not be able to set the route into the station/sidings. This is because it's expecting to set route from JP131 first, and it can't do that because a train is in the way.

Watford South Jn

This junction was, until the mid 2000s, located slightly further north. If you look at Google Earth or other satellite views, if the imagery hasn't been updated, it still shows the old layout.

Trains for local stations between Watford South Jn and Harrow-on-the-Hill must use the local lines here. Fast trains can use either the local or the main lines, though obviously the latter will be faster.

Moor Park

The only station on both the local and main lines between Watford South Jn and Harrow-on-the-Hill, this station sees some main line trains stop.

Northwood

This station has a storage siding, and can turn back trains towards London from its northbound platform. The storage siding also has an extension via a hand point but is not simulated here.

Harrow-on-the-Hill

This large station has six platforms, all electrified. Platform 2 is only electrified as far south as signal JB42 so while a southbound LUL train may arrive from the north, its only option is to turn back and head north again.

A reversing siding is provided north of platforms 4 and 5. Many trains from London terminate at Harrow-on-the-Hill and turn back via the siding.

There are four spring points here, denoted by the $ symbol. Routes set through these points will not show the point's position. Trains passing over the points in the trailing direction kick the blades over to the appropriate position if necessary.

Southern Boundary

The southern boundary between LUL and Network Rail is just to the north of Northwick Park station. However, the LUL and main lines continue to run alongside, or near, each other most of the way towards Marylebone.

Marylebone Contents

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Last edited by Steamer on 30/07/2020 at 14:43