Marylebone North Workstation

Introduction

This covers the area from Princes Risborough to Aynho Junction (exclusive) and the Aylesbury area. In 2015 it also controls the Bicester to Oxford (exclusive) section.

Locations

Princes Risborough

This station recently benefited from having the Up Through line restored to use. This allows Up trains (and Down, albeit at a lower speed), to pass through the station non-stop while avoiding the platforms. Flashing yellow aspects allow a higher speed approach from the Up Main in the Up direction to platform 2, and from the Down Main in the Down direction into the same platform.

Platform 1, a short bay platform, is usually used by shuttle services to & from Aylesbury.

Princes Risborough has a ten minute advance routesetting time for ARS. This means that ARS will set routes for trains up to 10 minutes before their departure time.

Bicester North

A reversing siding allows trains from the south to terminate here and form a new service back to the south.

ARS has been set up with no restrictions on setting routes early. This matches the real life IECC configuration.

Aylesbury to Princes Risborough Branch

This single-track branch has an ABCL crossing between Little Kimble and Aylesbury - this has a Permanent Speed Restriction over it of only 20mph for passenger trains and 10mph for freight trains, in both directions.

Automatic routesetting is delayed at either end of this branch until the train strikes track circuits close to the signals at either end. This prevents locking up Aylesbury or Princes Risborough prematurely and without benefit to the train on the branch.

Aylesbury

Seven sidings, three platforms, a depot, and three sets of running lines converge here, forming quite a complex area. This therefore requires attention to detail as each platform has restrictions on which running lines and sidings trains can go to and from. It is quite feasible to get knotted here! Though ARS can handle many of the moves, it does need to be observed closely to prevent any irrecoverable situations before they happen, and to set routes that ARS is not allowed to set.

From signal ME398 to ME390 there is a warner route which is selected automatically if the full overlap is not available. However, adjacent signal ME300 does not have such a reduced overlap option.

Timetables often require more than one train to use a siding where there is no joining or dividing activity. Arrival and departure times of both trains should be checked to ensure a train is not trapped between the buffers and the incoming train which has an earlier departure time than the incoming train.

Aylesbury North Loop

Bidirectional loop mainly intended to allow freight trains to or from Claydon Junction to stop clear of the Up/Down Aylesbury whilst requesting or replacing the token - although passenger trains may also use this loop if necessary, but do not need a token if heading to or returning back from Aylesbury Vale Parkway station. The token machine is at the north (left) end, and so Down trains towards Claydon Junction will stop nearer to it to collect the token before proceeding onwards. Trains from Claydon Junction that need to drop off the token will stop at the south (right) end of the loop to do so, before proceeding onwards. As per real life, the timetable must include a stop at Aylesbury North Loop for token purposes; although when it comes to actually signalling such a train you may use either the main line or the loop for trains requiring use of said token machine.

Aylesbury Vale Parkway

A bay platform exists here for passenger trains from the south. The through line adjacent allows access to Claydon Junction, several miles to the north. A token is required for the through line; see Aylesbury North Loop for details.

Claydon Branch

This branch sees no regularly scheduled passenger services, though does see occasional passenger specials. Most freight trains down this way are to and from the waste depot at Calvert.

Up Trains

Up trains will request a token release while at Claydon Junction. They will not proceed onto the single line until that release has been given, which is given by left-clicking on the "Aylesbury-Claydon Token Release" circle. However, the token machine itself is located at Calvert: it is a short distance further on. Once that release has been given, the train will pass signal CN3 at Claydon Junction and proceed to the token machine at Calvert. The train will stop, the driver will get out, and he will take the token. The token being taken is shown on the screen with a solid red circle next to the "Token Out" label.

The train will then proceed past Aylesbury Vale Parkway and into Aylesbury North Loop where the token machines are located. You can signal the train through either the loop or the main line, but it will still stop at the Up end (right hand end) to place the token back in the receiving machine. The red "Token Out" indication will be extinguished when this is complete. The token, and thus the single line to/from Claydon is thus now available for the next train.

Down Trains

Down trains will request a token release while stopped at the down (left) end of Aylesbury North Loop. Trains can use either the main line or the loop but will stop to collect the token. The token release will be flashing white when requested: left click to grant the release. When the driver actually takes the token, the red "Token Out" circle will change to a solid red circle. The route from ME303 towards Calvert is available once the token has been taken.

The train will then proceed towards Calvert. It will stop and drop off the token in the token machine, whereupon the red "Token Out" indication will return to a hollow red circle. The token, and thus the single line to/from Claydon, is now available for the next train.

'Race Conditions'

The signalling control simultaneously releases the token in all of the machines at once. It is therefore possible for a train to be waiting at each end of the single line to try to claim the token for themselves. Although only one will get it, it is unpredictable as to which will do so. Care should therefore be taken to ensure that only one train is within reach of a token machine at a time - and that usually means giving priority to Up trains from Claydon.

The token release indication will extinguish once a driver has taken a token. It does not remain lit while the train is in section.

Marylebone Contents

Last edited by Steamer on 30/07/2020 at 14:42