Rulebook procedures following failure of onboard AWS/TPWS

D365 · 20 Jun 2026

Picking up on the post below from the Bedford 19/06/2026 incident thread:

hwl said:
A key learning may be that coming to a halt in the shortest distance possible after a suspected AWS fault may not be the best practice as the following train could also be impacted by a trackside fault. Possibly better to slow and contact signaller while proceeding at low speed if the signals infront permit to reduce the risk of being rear ended.

Rulebook TW5 (Issue 10) states that, if AWS or TPWS is currently in operation, the driver must stop the train immediately and contact the signaller as soon as they become aware of a defect. The same also applies to defects relating to ATP, ETCS, DSD vigilance, horns or any mechanical / structural damage to the vehicles.

Notwithstanding the fact that the driver and signaller must come to a clear understanding before isolating any onboard systems, I don’t see how the driver of a defective train could be expected to diagnose the exact nature of a fault or defect with the train in motion.

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bengley · 20 Jun 2026

The 'stop the train immediately and contact the signaller as soon as they become aware of a defect' refers to defects with on-train equipment, not on-track equipment. If a right side (AWS horn at a green signal) fault is received, this does not require the driver to stop immediately, but report at a convenient location.

Indeed, if the driver encountered a fault with the on train equipment, which is entirely possible, they must stop immediately as per above.

Efini92 · 20 Jun 2026

bengley said:
The 'stop the train immediately and contact the signaller as soon as they become aware of a defect' refers to defects with on-train equipment, not on-track equipment. If a right side (AWS horn at a green signal) fault is received, this does not require the driver to stop immediately, but report at a convenient location.

Indeed, if the driver encountered a fault with the on train equipment, which is entirely possible, they must stop immediately as per above.

It doesn’t differentiate between on train equipment and track equipment in tw5.
A bell at a cautionary signal would require you to stop immediately and could be a fault with the electromagnet (the chances of which are highly unlikely) rather than the trains equipment.

bengley · 20 Jun 2026

Efini92 said:
It doesn’t differentiate between on train equipment and track equipment in tw5.
A bell at a cautionary signal would require you to stop immediately and could be a fault with the electromagnet (the chances of which are highly unlikely) rather than the trains equipment.

In order to understand the instruction you first have to bear in mind the purpose of the entire module

'Rule Book Module TW5 - Preparation and movement of trains: Defective or isolated vehicles and ontrain equipment'

== Doublepost prevention - post automatically merged: 20 Jun 2026 ==

The relevant module for an AWS magnet giving the wrong indication is S7 - Observing and obeying signalling indications. Train warning systems. Reporting signalling failures and irregularities.

And just below that on the next page: driver "Other AWS faults where the failure is to give a clear indication must be reported to the signaller at the first convenient opportunity. "

(Image contains a screenshot of the relevant rule book page)

Efini92 · 20 Jun 2026

Thanks for the lesson.

speciallygreen · 20 Jun 2026

Does it not add risk if the rule for receiving a clear indication when passing a cautionary signal is to stop immediately, potentially leaving the train in a section where a following train could also receive the same?

bengley · 20 Jun 2026

speciallygreen said:
Does it not add risk if the rule for receiving a clear indication when passing a cautionary signal is to stop immediately, potentially leaving the train in a section where a following train could also receive the same?

Actually a very valid point and not one I had considered.

357 · 20 Jun 2026

speciallygreen said:
Does it not add risk if the rule for receiving a clear indication when passing a cautionary signal is to stop immediately, potentially leaving the train in a section where a following train could also receive the same?

For all we know this is what happened yesterday...

I would still say personally that all signals should be fitted with at least trainstop loops. If that were the case, a red signal and the loops should stop anything nasty happening even if the magnet does have a wrongside failure

mrshed · 20 Jun 2026

I've been thinking about this myself, and posted on it a while ago in the other thread (which was fairly moderated out).
If this was a wrong side failure, the train (correctly) stopped.

If this failure was a wrong side failure due to an issue *track side*, this could give the same wrong side failure to the following train.

Now - that alone doesn't cause the accident, but if thats the case then it quite potentially removes all barriers to the crash bar one (which I will not speculate on here).

The key question I have (being a relative layman) is - is it a reasonably safe assumption, GIVEN that the train stopped, that this was a wrong side failure? It feels unfeasible that a clear and obvious train equipment fault (per the quoted handbook) could have been deduced in the timespan in question, which would be the other scenario that should cause a stoppage.

norbitonflyer · 20 Jun 2026

Efini92 said:
It doesn’t differentiate between on train equipment and track equipment in tw5.

Necessarily so, as there is no immediate way of distinguishing between a right side failure of the track equipment and a wrong side failure of the train equipment (or vice versa)

357 · 20 Jun 2026

mrshed said:
The key question I have (being a relative layman) is - is it a safe assumption, GIVEN that the train stopped, that this was a wrong side failure?

Whilst conveniently avoiding answering your question directly - I will add that some TOCs don't trust their drivers to use the GSMR on the move and demand a driver stops every time they need to speak to the signaller or the signaller needs to speak to them.

bengley · 20 Jun 2026

norbitonflyer said:
Necessarily so, as there is no immediate way of distinguishing between a right side failure of the track equipment and a wrong side failure of the train equipment (or vice versa)

A right side failure of the track and/or train equipment are the same thing - they will both result in a horn vice bell. Drivers up and down the country will tell you that in this scenario they will not stop to report it immediately. I would stop and report it if I encountered more than one or two right side failures in a row, which would either indicate a train fault or a problem with the infrastructure along a stretch of line

== Doublepost prevention - post automatically merged: 20 Jun 2026 ==

mrshed said:
I've been thinking about this myself, and posted on it a while ago in the other thread (which was fairly moderated out).
If this was a wrong side failure, the train (correctly) stopped.

If this failure was a wrong side failure due to an issue *track side*, this could give the same wrong side failure to the following train.

Now - that alone doesn't cause the accident, but the onward speculation of the single subsequent act that would need to take place is obvious (and I wont call it here, and it is exactly that - speculation). The point is that in this scenario, a wrong side failure as a result of an issue not on the train itself removed all barriers but one.

The key question I have (being a relative layman) is - is it a safe assumption, GIVEN that the train stopped, that this was a wrong side failure?

as 357 has said above - some companies ludicrously do not allow GSM-R use on the move. I am not sure whether EMR are one of these.

Other drivers may choose to stop to report things unnecesarily - this is not normally a problem other than an obvious delay being incurred.

mrshed · 20 Jun 2026

357 said:
Whilst conveniently avoiding answering your question directly - I will add that some TOCs don't trust their drivers to use the GSMR on the move and demand a driver stops every time they need to speak to the signaller or the signaller needs to speak to them.

Useful information - and more insightful than answering the question directly

thank you.

DNCharingX · 20 Jun 2026

I will echo the idea that if it’s a wrong side signal failure then the current rule book requirements are not good enough.

It should be an immediate REC because of the risk of the following train crashing into the rear at high speed.

In terms of AWS wrong side, as long as the train has not left the section before reporting it, should be fine, right? With emergency brakes you could probably stop within the overlap if not before the signal depending on speed.

Otherwise it’s a no win situation, stop and report, following train could crash, carry on, many other trains could crash into each other.

Slow down wouldn’t accomplish much as the accelerating train would still smack into the back presuming they had greens.

I see no win here. Even if every train in the area had to stop with wrong side AWS then you will have RECs come when trains have faulty onboard equipment.

hwl · 20 Jun 2026

speciallygreen said:
Does it not add risk if the rule for receiving a clear indication when passing a cautionary signal is to stop immediately, potentially leaving the train in a section where a following train could also receive the same?

That was exactly what was in my mind when I wrote the comment in the original thread that triggered this thread. (Some similarities with Clapham)

357 said:
I will add that some TOCs don't trust their drivers to use the GSMR on the move and demand a driver stops every time they need to speak to the signaller or the signaller needs to speak to them.

bengley said:
as 357 has said above - some companies ludicrously do not allow GSM-R use on the move. I am not sure whether EMR are one of these.

Which highlights the need for operational uniformity across operators with less "pick and mix" approach especially if stopping is usually but isn't always the safest option.

Traditionally drivers in many areas would have to proceed to the next signal to use telephone to contact the signaller (slight simplification to focus on better signalled areas) but now we have GSMR which gives them the opportunity to stop sooner/shorter and thus put less distance between them/the train and the fault.
Defining a suitable slow safe speed to move the leading train away from a trackside fault has effectively already been done already for PoSA (e.g. TL core).

More on PoSA here:

GERT8000-PoSA Iss 3 - Proceed-on-Sight Authority (PoSA)

You will need this module if your duties require you to identify and understand the meaning of PoSA signals. This document has be updated as part of the December 2015 Rule Book Programme.

www.rssb.co.uk

Calculating and using stopping distances normally assumes systems are fully functional and obeyed as a starting point, when you start to flex those assumptions you can get some very different answers...

Efini92 · 20 Jun 2026

mrshed said:
I've been thinking about this myself, and posted on it a while ago in the other thread (which was fairly moderated out).
If this was a wrong side failure, the train (correctly) stopped.

If this failure was a wrong side failure due to an issue *track side*, this could give the same wrong side failure to the following train.

Now - that alone doesn't cause the accident, but if thats the case then it quite potentially removes all barriers to the crash bar one (which I will not speculate on here).

The key question I have (being a relative layman) is - is it a reasonably safe assumption, GIVEN that the train stopped, that this was a wrong side failure? It feels unfeasible that a clear and obvious train equipment fault (per the quoted handbook) could have been deduced in the timespan in question, which would be the other scenario that should cause a stoppage.

Given the train involved is part of the 80x fleet I’d take aws fault with a pinch of salt. They have been plagued with faults ever since introduction. Mainly because far too much information is presented to the driver as fault, that is really just meant for maintenance teams.
Happy to be corrected though when the official report comes out.

norbitonflyer · 20 Jun 2026

bengley said:
A right side failure of the track and/or train equipment are the same thing - they will both result in a horn vice bell.

Not necessarily. If the line is clear and the AWS is working, but the signal is at fault, it could result in a bell but a non-green aspect - or no signal aspect at all.

King Lazy · 20 Jun 2026

Ive edited this as my original post included the possibility of missing an AWS magnet but from what I’ve seen the 810 seemed to be on greens so unless any temporary equipment was present that is unlikely. The 810 driver may have been surprised by a right side ‘horn instead of bell’ and missed cancelling but until the report we won’t know.

That said I want to address modern trains having an emergency application approaching a signal.

I’m going to talk about TPWS even though I’m aware it wasn’t fitted at this signal.

Modern passenger train brakes can be surprisingly good. They can often stop in a single signal section from 100+.

An emergency application occurring at a AWS magnet on approach to a signal could leave the rear vehicle of the train very close to the signal in rear. but just beyond the overlap allowing the signal behind to be cleared. Combine that with the acceleration of modern EMUs and a following train could reach considerable speed and potentially the two together could ‘outpace’ the original specifications of TPWS where fitted and quickly create a potentially dangerous situation where it isn’t.

I can think of a few places on my routes where a 10/11 car formation missing a magnet, tripping an OSS or anything else that initiates an emergency/heavy brake application approaching a signal could result in it pulling up easily within a single signal section. That could be not far round the corner from a signal. It would be easy for a following departure to hit 55-60 before encountering even an OSS grid on approach to the signal.

MarkWi72 · 20 Jun 2026

Will there be any Railcam footage of this? The trains were on the Bedford Cam section (Sth Junction). It may give a clue regarding linespeeds etc.

MatthewHutton · 20 Jun 2026

There’s probably sometime to be said for proceeding at a speed slow enough to stop visually?

357 · 20 Jun 2026

MatthewHutton said:
There’s probably sometime to be said for proceeding at a speed slow enough to stop visually?

Sorry, are you suggesting trains should always be able to stop visually? Your wording is slightly vague!

MatthewHutton · 20 Jun 2026

357 said:
Sorry, are you suggesting trains should always be able to stop visually? Your wording is slightly vague!

No, because that would massively restrict speeds. But there’s an argument in an emergency situation that staying in a broken block or whatever isn’t great - and that proceeding slowly is a good compromise.

357 · 20 Jun 2026

MatthewHutton said:
No, because that would massively restrict speeds. But there’s an argument in an emergency situation that staying in a broken block or whatever isn’t great - and that proceeding slowly is a good compromise.

As a driver who could be on either train I prefer the emergency call option. Stop everything, work out where the problem is, restart everything else, and go from there.

D365 · 20 Jun 2026

Efini92 said:
Given the train involved is part of the 80x fleet I’d take aws fault with a pinch of salt. They have been plagued with faults ever since introduction. Mainly because far too much information is presented to the driver as fault, that is really just meant for maintenance teams.

A failure of the onboard AWS/TPWS is presented to the driver by means of a ’simple’ fault indication.

didcot_watcher · 20 Jun 2026

mrshed said:
I've been thinking about this myself, and posted on it a while ago in the other thread (which was fairly moderated out).
If this was a wrong side failure, the train (correctly) stopped.

If this failure was a wrong side failure due to an issue *track side*, this could give the same wrong side failure to the following train.

Now - that alone doesn't cause the accident, but if thats the case then it quite potentially removes all barriers to the crash bar one (which I will not speculate on here).

The key question I have (being a relative layman) is - is it a reasonably safe assumption, GIVEN that the train stopped, that this was a wrong side failure? It feels unfeasible that a clear and obvious train equipment fault (per the quoted handbook) could have been deduced in the timespan in question, which would be the other scenario that should cause a stoppage.

We perhaps need to remember Clapham. Driver stopped to report a faulty signal, that failed to protect his train.

skyhigh · 20 Jun 2026

D365 said:
A failure of the onboard AWS/TPWS is presented to the driver by means of a ’simple’ fault indication.

Is that definitely the case? On CAF units an AWS/TPWS fault will also produce TCMS alarms (and spurious faults were pretty common when the units were new).

Efini92 · 20 Jun 2026

D365 said:
A failure of the onboard AWS/TPWS is presented to the driver by means of a ’simple’ fault indication.

Just out of interest have you been on any modern stock built in the last decade?

357 · 21 Jun 2026

D365 said:
A failure of the onboard AWS/TPWS is presented to the driver by means of a ’simple’ fault indication.

Do you mean the TMS categorises it as simple? Most stock I have signed in my career has had some sort of level 1/level 2 or yellow/red fault ordering on the TMS but any safety systems have always been in the more severe category that needs immediate intervention by the driver

flitwickbeds · 21 Jun 2026

Can someone describe what "wrong side" and "right side" failures are, and how they differ/present themselves?

66701GBRF · 21 Jun 2026

A right side failure is where there is a fault but it has failed at a safe level or hasn't compromised safety. Think of a track circuit showing occupied when clear and the protecting signal is automatically held at danger, that is a right side failure. A wrong side failure decreases the level of safety so with the scenario above, if the protecting signal still showed a proceed aspect with the track circuit showing occupied when clear then that would be a wrong side failure.

Right=Good
Wrong = Bad

Rulebook procedures following failure of onboard AWS/TPWS

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