New RSSB standards for speed signs

[Meerkat]

A recent issue of Modern Rail mentioned something about a change to standards allowing drivers to accelerate when the front of their train reaches a PSR sign, rather than waiting for the rear of the train to reach it.
I assume it must be more complicated than that as you wouldn’t want them doing it in a long stone train crossing a weak bridge etc. Is it a new variant of speed sign only for places where the PSR is about sighting - ie signal sighting or pedestrians at a UWC?

 

[XCTurbostar]

I believe these already exist as speed signs with an 'A' sign underneath?

Example here at Bristol Temple Meads: https://flic.kr/p/2qnAMnQ

 

[coxxy]

The A sign that has been trialled recently is being added to the rule book for permanent use as of December.

It's used predominantly when a TSR is in place for sighting reasons, so allows the driver to accelerate as soon as they reach the Teemination sign.

 

[trundlewagon]

I believe these already exist as speed signs with an 'A' sign underneath?

Example here at BRI: https://flic.kr/p/2qnAMnQ

I think the A boards at the end of TSRs (for crossing sighting purposes) have been A Thing for a few years but the PSR version must've been a trial, as they're a new inclusion to the Rule Book from December.

 

[theageofthetra]

The A sign that has been trialled recently is being added to the rule book for permanent use as of December.

It's used predominantly when a TSR is in place for sighting reasons, so allows the driver to accelerate as soon as they reach the Teemination sign.

Well overdue, I sent this as a suggestion to Network Rail on a work course about 5 years ago

 

[Meerkat]

Thanks all. Presumably makes a big difference to a half mile long intermodal!

 

[Bald Rick]

Well overdue, I sent this as a suggestion to Network Rail on a work course about 5 years ago

You were 10 years behind me! Can’t beleive it has taken this long, although I understand it needed much consultation and risk assessment.

There has actually been provision for this for some time through a special note in the weekly operating notice. I can remember a weak bridge at Grand Junction Birmingham with a TSR on it being marked in the WON as “loco hauled passenger trains may resume linespeed as soon as the locomotive has passed the T board“

 

[coxxy]

There used to be a TSR bear Ashton Under Lyne that had the speed commencement and the T on the same post as well, along with an instruction that the driver could accelerate as soon as they passed it.

 

[Ian Umpleby]

Signs introduced at Bradford Forster Square this weekend

 

[M1544]

Signs introduced at Bradford Forster Square this weekend

Those A boards would also be useful for departures from Bradford Interchange as they are on an uphill gradient from a standing start.

 

[edwin_m]

Those A boards would also be useful for departures from Bradford Interchange as they are on an uphill gradient from a standing start.

It depends on the reason for the restriction. In most cases, such as pointwork and curvature, the train will still have to keep to that speed until all of it has passed the end of the restriction. It's probably only restrictions relating to sighting (of signals and crossings) where the A will be used.

 

[zwk500]

Signs introduced at Bradford Forster Square this weekend

As Forster Square is a terminus with (I thought) relatively straight platforms, what is the reason for the A sign in that location?

 

[greaterangrier]

From my understanding of RSSB standards, the risk assessment for PSRs applies only to speed restrictions due to signal sighting. This means the permanent speed restrictions at some OMSL foot crossings will apply until the back of the train has passed still - very annoying given they have approved it for the TSR case.

 

[Taunton]

You were 10 years behind me! Can’t beleive it has taken this long, although I understand it needed much consultation and risk assessment.

There was a significant accident in early 25kV electrification days at Bethnal Green where the full-length train accelerated on a sharp curve once the front passed an increased speed sign, and the rear vehicles derailed and overturned. Had never been possible with previous traction. I seem to recall a number of measures came from this.

 

[306024]

Gypsy Lane foot crossing ‘temporary’ speed restriction, just north of Needham Market on the GEML has had an A board on the down line for some time, possibly the first location trialled?

As the TSR is for sighting, (foot crossing users sighting the approaching train), then once the train is on the crossing it has served its purpose. I believe the idea was pushed by GA as part of the Norwich in 90 aspirations.

Seems the principle has now extended to PSRs too.

 

[rower40]

As Forster Square is a terminus with (I thought) relatively straight platforms, what is the reason for the A sign in that location?

Devil's advocate: if the sign didn't have an A on it, what speed would the driver have to control their train to, until the entire train were past the sign? It would have to be the arrival speed of 20mph. The tail of a departing train doesn't have to be kept to 20mph (at least, not for platforms 1 and 2), so the A sign allows the train to accelerate as fast as physics/passenger comfort allows.

 

[Meerkat]

From my understanding of RSSB standards, the risk assessment for PSRs applies only to speed restrictions due to signal sighting. This means the permanent speed restrictions at some OMSL foot crossings will apply until the back of the train has passed still - very annoying given they have approved it for the TSR case.

That’s crazy, and the sort of thing that gives the system a bad name.
How big a risk assessment does it need? What am I missing - if the restriction is for user sighting at a crossing what possible need is there for it once the front of the train has reached the crossing?

 

[edwin_m]

Devil's advocate: if the sign didn't have an A on it, what speed would the driver have to control their train to, until the entire train were past the sign? It would have to be the arrival speed of 20mph. The tail of a departing train doesn't have to be kept to 20mph (at least, not for platforms 1 and 2), so the A sign allows the train to accelerate as fast as physics/passenger comfort allows.

Yes, clearly there is no reason why the part of the train within the platform has to remain at whatever the platform speed is (below 20mph). The reason may be something to do with signal sighting, but could it be that the TPWS doesn't provide adequate protection if a train passes the signal at a greater speed than the platform speed? This is only a concern until the train has passed the signal and TPWS loop.

 

[The exile]

From my understanding of RSSB standards, the risk assessment for PSRs applies only to speed restrictions due to signal sighting. This means the permanent speed restrictions at some OMSL foot crossings will apply until the back of the train has passed still - very annoying given they have approved it for the TSR case.

This seems daft, as once a train has reached the crossing, the speed it is doing is unlikely to cause any increased risk (unless other local factors are also involved).

 

[bluenoxid]

The local factor jumping to mind is local residents. Shifting the effective acceleration point after a speed restriction where there are loud 185/22x trains passing a property is going to be noticed.

 

[The exile]

The local factor jumping to mind is local residents. Shifting the effective acceleration point after a speed restriction where there are loud 185/22x trains passing a property is going to be noticed.

Obviously it makes a difference to individuals affected - but since all you’re doing is moving where the acceleration takes place by a few hundred metres max there will on average be as many winners as losers.

 

[greaterangrier]

An acceleration indicator shall be provided with a PSI only if the lower permissible
speed on the approach to the signal is necessary to mitigate signal overrun risk at
that location.

(my bolding)

I'm unsure why "only if" is here. The guidance part seems to contradict this suggesting that it can be applied to all cases unrelated to infrastructure limitations.

 

[Horizon22]

It does seem very sensible rather than drivers having to effectively take an 'educated guess' where the end of the train is and takes account for all types/lengths of rolling stock

 

[Meerkat]

(my bolding)

I'm unsure why "only if" is here. The guidance part seems to contradict this suggesting that it can be applied to all cases unrelated to infrastructure limitations.

Do they not have proof readers, nor give it to someone unconnected with the project and ask them if it’s clear what they mean?

 

[edwin_m]

It does seem very sensible rather than drivers having to effectively take an 'educated guess' where the end of the train is and takes account for all types/lengths of rolling stock

They will still have to do this for any speed changes that don't have the A on them, and the vast majority don't qualify because the reason for the speed restriction applies until the rear of the train passes the sign. Most modern freight locomotives have a distance counter that can be pre-set to the train length and started on passing the increased speed sign to indicate when the tail of the train is clear.

 

[InkyScrolls]

With Bradford I don't really understand why the A boards are being used on platforms 1 and 2 - we were able to accelerate straight up to 35 mph from a stand as it was. Possibly for consistency with platform 3, which was 15 mph until the whole train had passed the 20 mph board.

 

[Scotrail88]

Has there been any other sightings of the A boards?

 

[507 001]

We’ve just introduced A boards on Metrolink.

 

[Scotrail88]

We’ve just introduced A boards on Metrolink.

It helping when on double trams?

 

[507 001]

It helping when on double trams?

Very much so!