Speed restriction sign query

[Snow1964]

I have noticed that southbound just before Dundas Aquaduct (south of Bath on Westbury route) there is a double speed limit sign. Top one has 40 and horizontal bar with 60, and below it is one with SP 70 (on two lines).

So effectively 3 speed limits on same piece of plain (no junctions) track.
I wondered how common triple speed limits are

My main query is I have now realised there is an advance warning (the ones with yellow border and triangular bottom) some distance before, with same text, on two signs above each other on same pole. However I am sure I have read that these are only placed where speed limit reduces by about a third, so if there is a SP70 advance warning, it suggests Sprinters would be doing 105mph

The line uses 158, 165, 166 sprinters (which have 90mph max) so SP70 advance warning seems overkill. Is the SP70 only there to complete the set, and are there any other examples of SP70 advance speed restrictions.

There is a weekly train (early Saturday mornings) where an XC 220 or 221 Bristol-Taunton is routed this way, which of the 3 limits applies to it?

Hopefully someone can answer, Thanks

 

[greatkingrat]

The speed limit goes from 60/SP70 to 40/60/SP70. So it is only freight trains that have to slow down for the aqueduct and 60 to 40 is a third hence the advance warning. The warning sign still needs to show all three limits, otherwise it would look like all trains had to slow down to 40.

 

[lammergeier]

Voyagers can't do SP speeds so would be restricted to 60

 

[contrex]

165 and 166 classes aren't 'Sprinters', are they? I thought they were Networker Turbos.

 

[Tomnick]

Is the SP70 only there to complete the set, and are there any other examples of SP70 advance speed restrictions.

There's an SP85 advance warning board between Edale and Earles in the Hope Valley (70/SP90 reducing to 70/SP85). It's on its own too, as it is at the speed change itself, in that there's no board indicating the 70mph permissible speed for other trains.

 

[Darandio]

165 and 166 classes aren't 'Sprinters', are they? I thought they were Networker Turbos.

SP on a speed sign doesn't actually correlate with what is described as a Sprinter class of train. The following can adhere to SP limits.

150/153/155/156/158/159/165/166/168/170/171

 

[Wilts Wanderer]

Full signage (I.e. all reductions of speed advance-warned) is required on routes with linespeeds above 60mph. In practice most routes now have full signage regardless.

I believe the maximum number of variable speeds on any given piece of line is limited to 3, so Dundas is an example of this. Anything beyond that is determined to be too difficult for drivers to interpret at linespeed. In theory future installations of ETCS signalling could remove this limitation.

In practice I believe the limit of 3 led to some technical reductions of linespeed for certain traction types at certain locations on the WCML when the Enhanced Permissible Speeds (i.e. Tilt speeds) were introduced, as non-tilting trains now only had two options rather than 3.

 

[Railsigns]

Full signage (I.e. all reductions of speed advance-warned) is required on routes with linespeeds above 60mph.

It isn't. That's not to say that it doesn't happen on some routes, but it's not a requirement laid down in standards.

 

[Efini92]

It isn't. That's not to say that it doesn't happen on some routes, but it's not a requirement laid down in standards.

When warning boards were introduced wasn’t it that there was a warning for any 33% or more reduction in speed where the linespeed is 60mph or higher?

I have noticed that southbound just before Dundas Aquaduct (south of Bath on Westbury route) there is a double speed limit sign. Top one has 40 and horizontal bar with 60, and below it is one with SP 70 (on two lines).

So effectively 3 speed limits on same piece of plain (no junctions) track.
I wondered how common triple speed limits are

My main query is I have now realised there is an advance warning (the ones with yellow border and triangular bottom) some distance before, with same text, on two signs above each other on same pole. However I am sure I have read that these are only placed where speed limit reduces by about a third, so if there is a SP70 advance warning, it suggests Sprinters would be doing 105mph

The line uses 158, 165, 166 sprinters (which have 90mph max) so SP70 advance warning seems overkill. Is the SP70 only there to complete the set, and are there any other examples of SP70 advance speed restrictions.

There is a weekly train (early Saturday mornings) where an XC 220 or 221 Bristol-Taunton is routed this way, which of the 3 limits applies to it?

Hopefully someone can answer, Thanks

Here’s a list of what trains can use which differential speed. The only one missing is EPS which is for class 390 & 221 with working TASS.

 

[Railsigns]

When warning boards were introduced wasn’t it that there was a warning for any 33% or more reduction in speed where the linespeed is 60mph or higher?

That's the current requirement (the original requirements were slightly different).

It's permitted to provide additional warning indicators that don't meet these fitment criteria, and these ones don't need to be fitted with AWS.

== Doublepost prevention - post automatically merged: 3 Aug 2022 ==

SP on a speed sign doesn't actually correlate with what is described as a Sprinter class of train. The following can adhere to SP limits.

150/153/155/156/158/159/165/166/168/170/171

The applicability of "SP" speeds differs from one area to another. There's no national definition.

 

[Flange Squeal]

That's the current requirement (the original requirements were slightly different).

Do we know of many that have seemingly slipped through the net? A route I drive over (half-hourly service) has a 60 that drops to a 20 for a sharp curve and junction. In the near two decades I’ve been working the line, it’s never had a warning board!

I’m absolutely not saying you are incorrect - just genuinely curious if any fellow members have (m)any such examples of hefty drops without warnings on their patches, or if we just have a bit of an oddity!

 

[Efini92]

Do we know of many that have seemingly slipped through the net? A route I drive over (half-hourly service) has a 60 that drops to a 20 for a sharp curve and junction. In the near two decades I’ve been working the line, it’s never had a warning board!

I’m absolutely not saying you are incorrect - just genuinely curious if any fellow members have (m)any such examples of hefty drops without warnings on their patches, or if we just have a bit of an oddity!

It’s because it’s 60, if it was over 60 there’d be a warning board.

 

[Wilts Wanderer]

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I’ve attached the relevant extract from RIS-0734-CCS, dated Dec 2018, which I believe is the current version of the standard. Sourced from the RSSB online standards archive.



So to my understanding continuous signage is required for linespeeds of 60mph or more, and PSWI (advance warning boards) required for reductions of 1/3 or greater.

 

[Flange Squeal]

It’s because it’s 60, if it was over 60 there’d be a warning board.

Sounds like the standards are applicable to speeds “60mph or greater” rather than ‘over 60mph’?

 

[Efini92]

Sounds like the standards are applicable to speeds “60mph or greater” rather than ‘over 60mph’?

Yes my mistake, perhaps it’s just been missed?

 

[JN114]

If it was set up that way before standards said they had to provide a warning board, chances are one won’t be provided.

The standards are design standards; not what every line should be complying with every time they change.

 

[Wilts Wanderer]

If it was set up that way before standards said they had to provide a warning board, chances are one won’t be provided.

The standards are design standards; not what every line should be complying with every time they change.

I suppose in theory it’s also possible to justify a deviation from the standards. They’re guidelines rather than strictly enforced rules.

 

[Railsigns]

So to my understanding continuous signage is required for linespeeds of 60mph or more

How do you define "continuous signage"?

 

[Wilts Wanderer]

How do you define "continuous signage"?

I probably misused the phrase. I was meaning routes where PSWI boards are provided for all reductions in speed, regardless of linespeed.

 

[Railsigns]

So to my understanding continuous signage is required for linespeeds of 60mph or more, and PSWI (advance warning boards) required for reductions of 1/3 or greater.

A PSWI is required where the permissible speed on approach is 60 mph or more and the speed reduction is 1/3 or greater.

What you're calling 'continuous signage' (PSWIs for every reduction in permissible speed) isn't required anywhere, although it does exist on some lines.

 

[CC 72100]

That's the current requirement (the original requirements were slightly different).

It's permitted to provide additional warning indicators that don't meet these fitment criteria, and these ones don't need to be fitted with AWS.

== Doublepost prevention - post automatically merged: 3 Aug 2022 ==


The applicability of "SP" speeds differs from one area to another. There's no national definition.

Indeed - there was a time when Turbos could run at SP speeds on Western region, but not in Wales.