neilw
now that's what I call a garden railway
Posts: 284
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Post by neilw on Feb 7, 2009 15:25:02 GMT
Sorry to ask a basic question, but this has always puzzled me  At the end of a speed restriction, there is a "T" sign indicating the SR is terminated. Does this mean that the end of the last car has to pass the sign before speed can be increased, and if so, how can the train length be safely judged. If it indicates to the driver the point at which he can wind up, presumably it has to reflect the longest train length to be expected on the line (thinking back to uncoupling days.) |
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Deleted
Deleted Member
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Post by Deleted on Feb 7, 2009 15:51:01 GMT
A Driver cannot accelerate from a speed restriction until he has judged the last vehicle to have passed the T Board.
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Post by Tubeboy on Feb 7, 2009 15:52:44 GMT
Yes, the last car has to pass the T board.
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Colin
Advisor
My preserved fire engine!
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Post by Colin on Feb 7, 2009 16:15:34 GMT
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Post by Tubeboy on Feb 7, 2009 16:30:45 GMT
On Network Rail it is the back of the train - on LU it is the front actually   Is that because mainline drivers are better at judging distances? ;D I suppose in tunnel sections, judging a train length is harder than when in an open air section. |
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metman
Global Moderator
5056 05/12/1961-23/04/2012 RIP
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Post by metman on Feb 7, 2009 17:04:30 GMT
Also train lengths on NR also vary more.
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Deleted
Deleted Member
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Post by Deleted on Feb 7, 2009 17:20:17 GMT
On Network Rail it is the back of the train - Same on the Iarnrod Eireann and Northern Ireland Railway networks. |
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Colin
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My preserved fire engine!
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Post by Colin on Feb 7, 2009 17:20:50 GMT
Exactly right metman - trains on Network Rail can be anything from a single loco to a mile long freight train, so to accommodate the varying train lengths, it's always the back- and yes, it's down to driver judgment.
On LU, all passenger trains on a given line are the same length*; engineering trains are generally always the same length or shorter than passenger stock, so the termination point of a speed restriction can be accurately placed.
*= obviously there are exceptions such as the Chesham shuttle, but being shorter than the main passenger train service, it's existence is irrelevant.
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Post by citysig on Feb 7, 2009 20:27:48 GMT
In this post the "reason" (mentioned frequently) points to the problem/defect requiring restriction. This kind of sums up what has already been said, but anyway...
When restrictions are placed on LU, the signage takes into account the (average) length of trains passing through. The "T" board is placed a sufficient distance from the "reason" of the restriction, so that any train will be clear of the "reason" before resuming line speed. So for an outsider, it is often difficult to see what the "reason" for the restriction is.
On NR, the signage is placed exactly where the "reason" is. The restriction starts at the beginning of the "reason" and the "T" board is placed at the end. So for an outsider, it can be quite easy to see what the "reason" is. For example, signage may surround a set of points, leading the observer to guess that it may be those that are under restriction.
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North End
Beneath Newington Causeway
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Post by North End on Feb 7, 2009 22:29:37 GMT
A Driver cannot accelerate from a speed restriction until he has judged the last vehicle to have passed the T Board. There's an anomoly on the e/b District just east of Gunnersbury Junction. A newish LUL-type speed restriction board (LUL no longer uses "T" on new PSR signage, instead simply giving the speed for the next section) on the Network Rail section of track. So do you start accelerating at the board, or wait until the whole train has passed? Should the sign be a Network Rail red-border sign? |
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Colin
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My preserved fire engine!
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Post by Colin on Feb 10, 2009 1:00:17 GMT
The sign at Gunnersbury junction is technically incorrect (being an LU one on NR metals), however it replaced a NR sign and is as near as damm it in the right place such that we step up from 15mph to 30mph when the front of the train passes it - thus treating it as per LU rules.
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Post by mcmaddog on Feb 10, 2009 11:59:19 GMT
Exactly right metman - trains on Network Rail can be anything from a single loco to a mile long freight train, so to accommodate the varying train lengths, it's always the back- and yes, it's down to driver judgment. ON NR, locos such as 66s have a programmable computer where the driver inserts the length of the load before starting. As the loco passes a speed board the driver simply hits a button and the computer alerts the driver when the end of the train reaches that point. |
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Post by bassmike on Feb 10, 2009 13:22:16 GMT
I dont know where the T sign is leaving edgware road EB centre platform going west on wimbleware trains, but several occaisions while sitting in the rear car,the traversal of the scissors crossover was uncomfortable to say the least!
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