Caution signals approaching a booked stop

[MerlinRail 804]

If you’re approaching a station you’re booked to call at, and you get a double (or single) yellow signal, which indicates being cleared into the platform, but not out, do you slow down according to the signals and approach slowly, or just take note of it and brake in the normal way for the station?

 

[InkyScrolls]

If you’re approaching a station you’re booked to call at, and you get a double (or single) yellow signal, which indicates being cleared into the platform, but not out, do you slow down according to the signals and approach slowly, or just take note of it and brake in the normal way for the station?

Companies vary in their policies but at Northern we don't do more than 20 mph over an AWS magnet for a red. So if the signal is at the end of the platform that might mean entering slower than normal, yes.

 

[pokemonsuper9]

For some big stations like Manchester Victoria, trains will usually only get their clear signals once the dispatchers at the station press the TRTS (train ready to start), which then causes the signaller (or automated route setting) to set the route, in that situation, the usual stop will be with a red signal in front.

 

[800002]

You'd drive at the speed applicable for the signal.
They should know the permissible speed to which activation / intervention will occur if the driver is not adhering to the TPWS / AWS behaviours.

 

[RiverDon]

I get this at quite a few stations on the routes I drive (as a trainee). My company wants us to react to the double yellow/yellow signals in the normal way even if you know the red is at the far end of the platform you're stopping it. The policy at my place is for 15mph at the AWS magnet of the red signal, so if that's before the start of the platform then you'll be approaching slower than usual. In any case you need to press/call/react to the cautionary aspects and get your speed down well in advance of the red even if the normal braking point for the station is later than this. And remember to set the DRA!

 

[MerlinRail 804]

Glad I’ve been doing it right in TSW then!

They should know the permissible speed to which activation / intervention will occur if the driver is not adhering to the TPWS / AWS behaviours.

What are said speeds?

 

[357]

They should know the permissible speed to which activation / intervention will occur if the driver is not adhering to the TPWS / AWS behaviours.

At many TOCs, they deliberately do not tell the drivers the speed the racks are set at. Some years ago on the LTS they removed the signposts next to the racks that had the speed printed on them (I believe these are still visible in the Video 125 DEV)

== Doublepost prevention - post automatically merged: 3 Mar 2026 ==

I get this at quite a few stations on the routes I drive (as a trainee). My company wants us to react to the double yellow/yellow signals in the normal way even if you know the red is at the far end of the platform you're stopping it. The policy at my place is for 15mph at the AWS magnet of the red signal, so if that's before the start of the platform then you'll be approaching slower than usual. In any case you need to press/call/react to the cautionary aspects and get your speed down well in advance of the red even if the normal braking point for the station is later than this. And remember to set the DRA!

Yep, just a case of making sure you are within the driving policy at the platform ramp and at the magnet.

I tend to slow down to 30mph after a single yellow and let it roll - I won't go into TPWS speeds in this thread in too much detail but it is very rare to have a set of racks before the magnet set at less than 33mph

 

[Efini92]

If you’re approaching a station you’re booked to call at, and you get a double (or single) yellow signal, which indicates being cleared into the platform, but not out, do you slow down according to the signals and approach slowly, or just take note of it and brake in the normal way for the station?

Yes, the priority is driving to signals.
That scenario has caused countless tpws activations over the years.

 

[AverageJoe]

Depends where the magnet is for me. Could be a long platform and my stopping point is before the magnet. If that’s the case i plan my braking around the stopping point.

If the magnet is near the start of the platform then I will be slowing for that as per my company policy.

 

[LCC106]

You'd drive at the speed applicable for the signal.
They should know the permissible speed to which activation / intervention will occur if the driver is not adhering to the TPWS / AWS behaviours.

Our company won’t publish the speeds, although some are commonly known. You (general comment, not you personally) should be driving to the signals but consider platform stopping points.

The grids are often set at less than 33mph - in permissive or bay platforms for example.

I guess it may vary depending on routes?

 

[Annetts key]

The "set speed" of a TPWS overspeed sensor (OSS) system when provided for a "stop" signal is related to both the line speed and how far beyond the signal a train gets to a point of conflict, in other words, where the points or level crossing is/are.

The principal is that if a train is travelling at line speed, and the driver does nothing, then the TPWS OSS should activate the brakes such that the train stops short of the point of conflict or the speed is reduced to such a low level that any potential crash has a low risk of causing injuries.

However, as TPWS has to be suitable for all train types, the set speed is a compromise between affecting modern stock with modern braking systems and older stock with traditional braking systems. Hence why drivers of modern stock normally need to drive slower that they would have done before the introduction of TPWS.

 

[357]

Depends where the magnet is for me. Could be a long platform and my stopping point is before the magnet. If that’s the case i plan my braking around the stopping point.

If the magnet is near the start of the platform then I will be slowing for that as per my company policy.

I know a fair few people who've set racks off doing this exact thing.

 

[AverageJoe]

I know a fair few people who've set racks off doing this exact thing.

Well that completely depends on what the drivers typical approach speed to a platform is. Mine is always cautious.

 

[800002]

Our company won’t publish the speeds, although some are commonly known. You (general comment, not you personally) should be driving to the signals but consider platform stopping points.

The grids are often set at less than 33mph - in permissive or bay platforms for example.

I guess it may vary depending on routes?

Yes, much is going to depend on how the driver is taught to behave in such circumstances.

 

[357]

Well that completely depends on what the drivers typical approach speed to a platform is. Mine is always cautious.

It also depends where you drive. I've worked for TOCs where you could enter a platform at 50, and TOCs where if you enter at much more than 20 you risk not stopping in time.

 

[Archvile]

If it's a red at the end, drive to the signal. If it's single yellow or better, I do my normal station approach.
If I know I have a red at the end which then clears to a single yellow, I'll take full power again to get back to my normal braking curve for the station.

 

[Falcon1200]

Our company won’t publish the speeds, although some are commonly known.

Which is something (as a Network Rail Controller, not Driver!) I found strange right from the introduction of TPWS. Especially as a number of activations occurred at Permanent Speed Restrictions (PSRs), until Drivers became used to the settings. I have never understood why the settings could not be published, given that braking points can vary depending on, for example, weather/rail conditions, train/unit type and performance.

 

[InkyScrolls]

Which is something (as a Network Rail Controller, not Driver!) I found strange right from the introduction of TPWS. Especially as a number of activations occurred at Permanent Speed Restrictions (PSRs), until Drivers became used to the settings. I have never understood why the settings could not be published, given that braking points can vary depending on, for example, weather/rail conditions, train/unit type and performance.

As a driver I quite agree, as do all other drivers I've spoken to. They are essentially a hidden speed limit.

 

[trentside]

Which is something (as a Network Rail Controller, not Driver!) I found strange right from the introduction of TPWS. Especially as a number of activations occurred at Permanent Speed Restrictions (PSRs), until Drivers became used to the settings. I have never understood why the settings could not be published, given that braking points can vary depending on, for example, weather/rail conditions, train/unit type and performance.

A reason I’ve been given is a concern drivers will then driver to adhere to what the TPWS is set at rather than focusing on ensuring they’re compliant with the PSR. Not sure I agree with this personally, and the set speed often becomes common knowledge after an incident anyway.

 

[Falcon1200]

Not sure I agree with this personally, and the set speed often becomes common knowledge after an incident anyway.

Indeed, and if they are complying with the TPWS speed, that is lower than line speed so they are already braking!

 

[Sheridan]

Indeed, and if they are complying with the TPWS speed, that is lower than line speed so they are already braking!

I do agree with you broadly, but I think the point is that they may get down to the set speed, let’s say 68 at the grids for a 60 PSR (as an example, I don’t know what it’s likely to be set at) and then continue on at that speed rather than getting down to 60. The grids become the target when it should be the PSR.

 

[Annetts key]

I do agree with you broadly, but I think the point is that they may get down to the set speed, let’s say 68 at the grids for a 60 PSR (as an example, I don’t know what it’s likely to be set at) and then continue on at that speed rather than getting down to 60. The grids become the target when it should be the PSR.

For PSR installations, the TPWS OSS is on the approach to the PSR, but after the Advance Warning Indicator (AWI), hence normally the set speed is less than the line speed where it is located, but higher than the PSR value.

As a diagram:

    AWI            PSR
     ⚠    OSS     [40]
-----------==-------------> direction >

As an example, if the line speed (or attainable speed which is what is used in the design calculations) is 90MPH, the PSR is 40MPH, then the TPWS set speed will be somewhere around 80MPH.

Hence I would recommend that drivers drive more cautiously to ensure they are travelling below the TPWS OSS set speed but in any event ensure that at the PSR commencement board, you have slowed to comply with that speed restriction. The TPWS OSS "grids" or "racks" (officially called loops) should not form a target for drivers. The PSR commencement board is the target.

 

[Falcon1200]

Hence I would recommend that drivers drive more cautiously to ensure they are travelling below the TPWS OSS set speed

Indeed, but how does a Driver know what that set speed is, other than by experience (of them and others)! It is surely possible, on a dry day with a good set and a confident Driver, to exceed the OSS setting while still being at or below the PSR speed at its start.

The PSR commencement board is the target.

Yes of course.

 

[Annetts key]

Indeed, but how does a Driver know what that set speed is, other than by experience (of them and others)! It is surely possible, on a dry day with a good set and a confident Driver, to exceed the OSS setting while still being at or below the PSR speed at its start.

Although there were the occasional trip reported at PSR TPWS installations, the vast majority of TPWS trips that were reported in my area when I was S&T team leader were for TPWS OSS or OSS+ installations associated with TPWS fitted signals.

There were also a couple of buffer stop TPWS trips reported.

As I'm not a train driver, so I can't really give much advice other than to repeat that as TPWS is a compromise, drivers should consider what braking and speed reduction would be required for stock with the older type of braking system. That's what I meant by driving more cautiously. If you reduce your speed to give a greater margin of distance before the commencement board / before the signal at red / before the buffer stop, that will be more similar to the braking curve of older stock. Hence there is a much reduced chance of tripping the TPWS.

As many drivers have found, when driving a modern train (with a really good braking system) in dry conditions, they can brake later and still comply with the PSR / stop at the signal / stop short of the buffer stop. But get caught out by unintentionally tripping the TPWS.

Alas because of the design of TPWS, there is no straightforward technical fix to this problem. TPWS is fundamentally a "dumb" system (it's not computer based) in that it cannot differentiate between a loco and MK2 stock and a modern EMU/DMU etc. that has modern high performance brakes.

As a comparison, ATP and ERTMS/ETCS are computer based and the trains onboard computer can constantly recalculate the wanted braking curve vs. the current speed and braking performance.

 

[LCC106]

Which is something (as a Network Rail Controller, not Driver!) I found strange right from the introduction of TPWS. Especially as a number of activations occurred at Permanent Speed Restrictions (PSRs), until Drivers became used to the settings. I have never understood why the settings could not be published, given that braking points can vary depending on, for example, weather/rail conditions, train/unit type and performance.

I find this interesting!

 

[TreacleMiller]

Which is something (as a Network Rail Controller, not Driver!) I found strange right from the introduction of TPWS. Especially as a number of activations occurred at Permanent Speed Restrictions (PSRs), until Drivers became used to the settings. I have never understood why the settings could not be published, given that braking points can vary depending on, for example, weather/rail conditions, train/unit type and performance.

I annotate my route maps with TPWS OSS activation speeds when they are published in the incident reports so I have a record of them.

I spoke with a friend who is pretty senior in NR on the signalling side and he said that to his recollection the decision not to publish the OSS speeds seems to have been from a fear that it would encourage "at limit" driving to OSS speeds rather than create a healthy fear of them to encourage drivers to brake earlier for them.

Seems and odd one to me since they do eventually reveal the speed.

 

[greatkingrat]

The problem then is that as drivers don't know the speed, they end up driving unnecessarily cautiously, even though they are well under the OSS speed.

 

[Falcon1200]

Seems and odd one to me since they do eventually reveal the speed.

Indeed, and being caught overspeeding at the OSS does not automatically mean that the train would be overspeeding at the start of the PSR. But probably too late to worry about now!

 

[172007]

Indeed, and being caught overspeeding at the OSS does not automatically mean that the train would be overspeeding at the start of the PSR. But probably too late to worry about now!

We had a famous one up Old Hill Bank. The OSS had to be changed.

The PSR uphill goes from 60mph to 40mph. The OSS was set at such a low speed and the gradient being so steep that trains were triggering the OSS and coming to a stand with the driver still looking at the 40mph start board or a choach lenght past it.

 

[Tomnick]

The problem then is that as drivers don't know the speed, they end up driving unnecessarily cautiously, even though they are well under the OSS speed.

...and then inevitably having to release the brake and coast towards the PSR, well below the (unknown) OSS set speed but still above the PSR speed, with a significant risk of losing focus and failing to make the second brake application that's then required.