SimSig Wembley Suburban

Manual - release 2

Last modified 2014-12-11

Table of Contents

    Legal Stuff
Geographical Summary
    Electric Traction
    Other Operational Notes
Croxley era differences
Fringe Working
Train Service
    Main Movements
Timetable Locations
Hints and Tips
Known problems


Wembley Suburban has been written at the request of the manager of the real Wembley Suburban PSB and with the aid of detailed signalling diagrams. It should, therefore, be as accurate as practical.

Legal Stuff

SimSig is for personal entertainment use only and must not be used for any commercial use, including the training of signallers etc. Those who are interesting in the commercial application of this software should look at

SimSig is protected by copyright. No SimSig file may be distribution by any other website, by CD ROM or other media without express written permission from G. Mayo. The only exception is when SimSig files are transferred between private individuals where no charge, fee or profit is levied.

This software and is offered as-is, "what-you-see-is-what-you-get". Errors, omissions, faults or other problems are not covered by any warranty of any kind. Problem reports may be emailed or posted on the forums but action may or may not be taken by the authors, a decision which is up to said authors. SimSig accept no responsibility for any damage that may be caused to computer systems by the software.


As ever, my thanks to Geoff and Mike for teaching me how to write simulations, to all the people who provided information, and to the beta testers.

Thanks to Dan King Morrison for permission to use two of his photographs of the exit from Stonebridge Park depot as splash screens.


This version was written with access to official signalling plans giving track layouts, track circuit details, locations, overlap lengths, and gradients. Therefore all of these details are accurate. Note, in particular, that not all automatic signals have "passable" plates in real life and this is replicated on the simulation. Speed limits are taken from the Sectional Appendix. However, in some places train describer berths are merely "plausible" and have not been confirmed.

In general the simulation replicates the situation as of 2007, though with the option to have the extended platform 2 at Willesden Junction (note that when the platform was extended, signal 18 moved to the other side of the track). There is also the option to switch to the layout with the Croxley Green branch, before control was moved from the separate signal box to a workstation within Willesden signalling centre. Note that there were significant changes elsewhere in the controlled area at this time, so enabling the branch has other effects as well. In this manual these differences are described in terms of the "Croxley era" or the "modern era".

Even though "Queen's Park" would be more accurate, the name "Queens Park" is used in the simulation and this manual as it is what is found on the actual workstation and in various documents.

Geographical Summary

The area covered by SimSig Wembley Suburban follows the DC Lines (sometimes called the "New Lines") from Watford Junction south to just north of Camden Junction, where control passes to Wembley Mainline signalling centre. At Watford Junction there are connections to the main (AC) lines, and at Willesden Junction there is a branch to meet the North London Line at Kensal Green Junction. In the Croxley era, at Watford High Street there is a single-track branch to Croxley Green and Cardiff Road CEGB sidings.

The entire simulation (almost) fits into a single screen. It is divided into three "stripes". The boundaries between the stripes are protected by automatic signals, so it is never necessary to consider two stripes at once when handling trains. On all three stripes, the Up direction (southeast, towards Euston) is rightwards while the Down direction (northwest, towards Watford) is leftwards.

A quick guided tour follows. It is advisable to open SimSig Wembley Suburban and follow this tour.

Stripe 1: This runs from Watford Junction to Headstone Lane; the only controlled areas are Watford Junction station and, when the Croxley Green branch is included, Watford High Street station and the branch.

At Watford Junction the simulation chains to Simsig Watford Junction, which controls the main lines. Each box sets routes from its area to the other's in the normal way after a slot has been granted. The signals controlled by the other box can only be used for this purpose, and not as the starting point when setting a route. There is also an additional release to allow the crossover between the two boxes (531 points) to be reversed. These points can only be moved if this release or one of the two slots has been granted.

When the two boxes are not chained, sufficient extra lines and signals are displayed to allow trains to be brought in and out of the controlled area. The layout of these lines has been deliberately simplified, though the signals and trackwork used to enter and leave the sidings is accurate. These signals can be controlled in the normal way, though the slots must still be used. Trains can enter on the right hand side on either the Down Fast line (the line through platform 6) or from the Down Slow (not shown) via the Up Fast (the topmost line on the simulation); similarly they can leave to the left on the Down Fast or to the right on the Up Fast. As well as the sidings between the Down Fast and the Up DC, there are further sidings on the far side of the main lines, reached via the Up Fast; these are not shown.

The stop board for trains entering Cardiff Road CEGB sidings is located on the middle of the crossover, not at the end of the track circuit. When a train reaches the stop board, it will wait for instructions from the shunter and will then enter without further action from the signaller (unless, of course, there is a train waiting to exit, in which case you have a problem).

Stripe 2: This section covers the line from north of Harrow and Wealdstone to south of Stonebridge Park. Harrow is the northern terminus of the London Underground Bakerloo Line service. Most trains reverse in the centre siding, but it is also possible for a train to run directly south from platform 1 via the crossover.

The crossover at Wembley Central is controlled by a ground frame. In the modern era, the ground frame can only be released if both protecting signals are red with no route set from them, and no train is between the signal and the crossover. In the Croxley era, the protecting signals are semi-automatic: granting the release will put the signals back to danger even if a train is approaching them. Releasing the frame will cause two new ground signals to appear (these simulate a handsignaller - there are no signals there in reality). These signals are controlled from the ground frame levers 3 and 4.

Stonebridge Park is the access point for the LU depot. Both tracks are bidirectional, though normally 21 Road is used as the arrival line and 22 Road as the departure line. The two tracks then converge into a single one - the signals leading into the depot and the points on the convergence are controlled by the depot signalman and not Wembley Suburban. When a train is signalled towards the depot from Stonebridge Park station, the signal will only clear if there is an LU headcode (see below) beginning 'I' or 'S' in the relevant train describer berth. As an option, the simulation allows this to be turned off or to merely test for any LU headcode. The two yellow lamps are used by the depot staff to indicate which line the next train will appear. Note that they have been known to change their minds or accidentally use the wrong lamp.

Stripe 3: This runs from Harlesden to immediately before Camden Junction and includes the two key locations of Willesden Junction and Queens Park. The former gives access to Kensal Green Junction and thence the North London Line, plus the TMD, while the latter is the place at which Bakerloo Line trains enter and leave the controlled area, though they can also reverse at Kilburn High Road.

The bay at Willesden Junction is only 67 metres long (87 metres when lengthened).

Permission must be gained by telephone from Willesden TMD before sending a train there. Failure to get permission will be penalized. Willesden TMD will telephone for permission to enter a train. The signal box special instructions require that, before giving permission, signals 302, 16, and 18 must all have reminders applied. Failure to do this will also be penalized. They also require that the reminder on 302 is not removed until the driver has been asked to call back, and has done so, from the next red signal or from Willesden Junction platform 2. However, at present this is not enforced by the simulation.

Signal 8 will only clear for trains on to the Bakerloo Line if there is an LU headcode (see below) in the train describer berth (there is an option to remove this check) and they have fourth-rail power (there is a negative shoe detector approaching the signal - this cannot be overridden). Sources vary as to whether signal 8 has an auto button, so this is made an option.

If a train with an LU headcode is signalled towards Kilburn High Road from signal 4 (Queens Park Up line), signal 2 will revert to red and stay so until the train has reversed (more precisely, until signal 7 has been cleared and then the platform is unoccupied).

At Kensal Green Junction facilities have been included to chain to future releases of SimSig NLL. At Camden Junction this simulation chains to SimSig Euston.


The general speed limit over most of the line is 45mph with a few slower sections (such as 40mph through the tunnel south of Wembley Central, or 20mph southbound through Bushey station). However, this only applies to EMU stock fitted with tripcocks. All other passenger stock is limited to 25mph south of Harrow, while freight trains have a limit of 40mph north of Harrow and 15mph south of there. Most crossovers, sidings, and bays are 15mph.

Trains will only run at the higher speeds if either the "Metro" or "Tripcock" speed class is set in the train's timetable. Other speed classes may be set but will be ignored.

Electric Traction

As is obvious from the name, the entire DC lines are equipped with third rail DC. In addition, that part of the line used by London Underground trains is also equipped with fourth rail DC. At Harrow and Wealdstone, the fourth rail extends into the reversing siding and also along the Down Line (but not the Up Line) to a point level with its end. South of Queens Park, both tracks as far as the crossover, and then the Up Line platform at Kilburn High Road, have fourth rails. Stonebridge Park depot and the Bakerloo Line tracks at Queens Park are only equipped for fourth-rail trains; they cannot be used by third-rail EMUs.

At Watford Junction DC extends along the link to the Down Fast and thence to a point in platform 6 about 80 metres beyond signal WJ2006. The two main lines, but not the sidings or the link, are equipped with AC overhead.

The branch to Kensal Green Junction contains a changeover section from DC to AC. Thus only diesel trains and dual-equipped stock (such as class 313) can use it. The TMD is equipped for third-rail DC.

Other Operational Notes

The signal box special instructions state that routes must not be set from the following signals until TRTS has been given. A penalty will be imposed if this requirement is ignored.


The scenarios are self-evident.

Croxley era differences

The Croxley Green branch was removed from the signalling at the same time that the existing interlocking was replaced by a new electronic one. The opportunity was taken to make a number of other changes at the same time.

Fringe working

At any of the 10 places where a train can enter (three at Watford, two at Stonebridge Park Depot, Camden Junction, Queens Park, Kensal Green Junction, Willesden TMD, and Cardiff Road CEGB sidings), the fringe box can be told that the line is blocked by putting a special code into the relevant train describer berth:

Train Service

The supplied timetable is based on the workings of August 2006. It runs from 04:30 to 05:30 the following day (shown as 29:30), though the last timetabled move ends at 28:42.

There are a total of 687 schedules in the timetable involving 302 trains entering the simulation and 4 seed trains. The only divides are three of the seed trains; the only joins take place right at the end of the timetable.

I am advised that not even the real signallers can make this timetable run to time.


Standard railway descriptions (headcodes) are used for non-LUL trains. The first digit is the class of train. The second character is a letter, which usually denotes the route taken by the train. The remaining two digits simply give each train its own identity.

The only train classes used are 2 (Local Passenger Train) and 5 (Ordinary Empty Coaching Stock).

The route letters found in the timetable are as follows.

CWatford to Euston, plus ECS from both sets of sidings at Watford
DEuston to Watford, plus ECS to both sets of sidings at Watford
LTrains from the DC lines to the North London Line (while most of these exit at Kensal Green Junction, a few exit at Camden Junction)
MTrains from the North London Line to the DC lines (while most of these enter at Kensal Green Junction, a few enter at Camden Junction)

London Underground trains, however, use a description that has the route letter first followed by the train's 3-digit number, which it retains for the entire day. The class of train is not indicated. As a result, the same headcode will appear several times, as (say) train 223 becomes in sequence J223, K223, J223, K223, H223, S223, and so on. Within the supplied timetable, a suffix is used to distinguish these workings; this suffix always runs from 1 to 9 then A to U omitting I and O, irrespective of the first part of the headcode. For example, train 223 is in sequence J223-1, K223-2, K223-3, J223-4, K223-5, K223-6, H223-7, etc.

The route letters used by LU are as follows (note that some trains in the supplied timetable use the "wrong" letter):

Ato Elephant & Castle
Fto Queens Park (in service)
Hto Willesden Junction
Ito Stonebridge Park (in service)
Jto Harrow & Wealdstone (in service)
Kto Waterloo
Oto London Road depot (empty)
Pto Queens Park (empty)
Sto and from Stonebridge Park Depot (empty)
Tto Harrow & Wealdstone (empty)
Wto Kilburn High Road (empty)

Main Movements


Silverlink (now London Overground) run a regular service between Euston and Watford Junction calling at all stations. There are also a few services from Willesden Junction to the North London Line and vice versa, operated by class 313 dual-voltage EMUs, and a few ECS DMUs running to and from the TMD.

London Underground

The Bakerloo Line of London Underground runs a frequent service between Central London and Queens Park, with many trains extending to either Harrow and Wealdstone (usually, but not always, reversing in the siding) or Willesden Junction (and then ECS to and from Stonebridge Park Depot). There are also a number of ECS workings into and out of the depot, and some other odd workings.

Freight Services

There are no freight services in the timetable.

Timetable Locations

This section lists the internal codes (which in many cases are TIPLOC codes) for the timetable locations in the simulation, and also provides a brief description of the less-obvious locations. These codes are used when using the timetable converter.

When a train enters the simulation a different code - an entry point code - is used. These codes are shown in italics following a » symbol. In general, the entry location should not be the first location in the train's timetable as well.

ZWATDF Watford dep. north; use for trains departing northwards (to the left) along the Down Fast.
WATFDJ Watford Junction plat 6.
WATFJDC Watford Junction (DC); all four DC platforms.
WATFJCS Watford Junction sidings » EWJS.
WATFJSJ Watford south (reverse); signal 309, used only for reversing trains.
ZWATUF Watford dep. south; use for trains departing southwards (to the right) along the Up Fast » EWJDF or EWJDS (Down Fast and Slow lines respectively).
WATFDHS Watford High St.
SX71049 Cardiff Road CEGB Sidings » E71049.
WATFDSM Watford Stadium.
WATFDW Watford West.
CRXLYG Croxley Green.
CRPNDPK Carpenders Park.
HTCHEND Hatch End.
HEDSTNL Headstone Lane.
HROW307 Harrow siding.
HROWDC Harrow and Wealdstone.
HROW305 Harrow (south); signal 305, used only for reversing trains.
KTON Kenton.
SKENTON South Kenton.
NWEMBLY North Wembley.
WMBYGF Wembley Cent. (rev.); the down line immediately north of the emergency crossover.
WMBYDC Wembley Central.
STNBPKD Stonebridge Park LU depot (STNBD36 is also an acceptable alias) » ESPARR or ESPDEP (21 and 22 roads respectively).
STNBS34 Stonebridge Park depot entrance; signals 32 and 34 (STNBD32 is also an acceptable alias). Note that the TRTS indicators at these two signals will only be triggered by trains that have this location in their timetable.
STNBGPK Stonebridge Park; station.
HARLSDN Harlesden.
WLSD303 Willesden north (reverse); signal 303, used only for reversing trains.
WLSDNJL Willesden Junction.
KENSLGJ Kensal Green Junction » EKGJ.
WLSD301 Willesden south (reverse); signal 301, used only for reversing trains.
KENSLG Kensal Green.
QPRKJ Queens Park Junction
QPRK Queens Park; both trains through to Camden Junction and those going on to the Bakerloo Line » EBAKLOO.
KLBRNHR Kilburn High Road.
SHMPSTD South Hampstead.
CMDNJN Camden Junction » ECAMDJN.

Hints and Tips

If you're doing anything odd, don't forget the train-describer-based controls at Stonebridge Park and Queens Park.

Known problems