Can a train operate in passenger service with the AWS isolated?

[NoOnesFool]

Hello all. I was reading about a train crash which sadly ended in the loss of 7 lives in West London. Part of the cause of it was that the Automatic Warning System (AWS) was isolated on the driving car and several signals were passed without the aspects being noticed, it seems. I was surprised to read that it was permissible for trains to operate with the AWS isolated. Is it still allowed in this day and age? Would a secondman be needed for an additional look out?

 

[DanNCL]

A 50/60mph limit (can’t remember which) applies to all stock without working AWS unless a second competent person is present in the cab.

Working AWS is not required for lines equipped with ETCS or TVM signalling, as such in theory a 395 with defective AWS could run unrestricted on HS1.

 

[Teddyward]

60/40(poor visibility)
Isolating AWS will also knock out TPWS on most stock I imagine.
Realistically what should happen is, work to next suitable place to be taken out of service, detrain and return empty to depot.

 

[D365]

Isolating AWS will also knock out TPWS on most stock I imagine.

Full isolation of a Mk4 TPWS system would definitely do that. Not sure about the temporary isolation toggle switch.

 

[norbitonflyer]

I assume this is the accident in question https://www.railwaysarchive.co.uk/documents/HSE_Southall1997.pdf
It is now quarter of a century ago. You are right that "the past is a different country where they do things differently".

The AWS failure was first reported the previous day but the maintenence depot were unable to replicate it. It was not noticed on the way to Swansea as the affected cab was then at the rear. The train could have been turned on the triangle at Swansea to get it back to London with an opedrational AWS in the leading cab, that that would have cost time and led to financial penalties.

Changes introduced as a result of Southall included a requirement for a second competent person in the cab or a severe speed limit. TPWS has also been introdced, but of course there have to be procedures in place should that fail.

Three of the carriages towards the rear of the train 42073+42074+44024, along with the rear power car, suffered only minor damage and were repaired and put back into service. The same carriages (but not the same power car) were again at the rear of the HST involved in the Ladbroke Grove crash two years later and were again eventually repaired and put back into service.

A similar coincidence of survival befell loco 91023, which was leading the train that derailed at Hatfield in 2000 (the loco was undamaged as the derailment happened further back down the train) and again largely undamaged when at the rear of the train in the Great Heck crash the following year. Subsequently renumbered 91132.

 

[hexagon789]

I was surprised to read that it was permissible for trains to operate with the AWS isolated.

It was in many quarters argued that it was an advisory system, given that if an AWS warning is acknowledged by the driver it takes no further action you can perhaps appreciate this point of view.

As it is, I remember in Video125's Northern Lights driver's eye view that the AWS failed part way en route to Aberdeen from Edinburgh. The narrator notes that in such circumstances the driver is permitted to continue at full linespeed except in poor visibility - it was filmed in 1996 I believe.

 

[dan4291]

Linespeed if you have a competent person with you and good visibility, 60 if no competent person and good visibility, 40 if poor visibility (with or without a competent person).

 

[hexagon789]

Linespeed if you have a competent person with you and good visibility, 60 if no competent person and good visibility, 40 if poor visibility (with or without a competent person).

I don't think that applied pre-Southall.

Certainly no "competent" person accompanied the driver in the cab after the AWS failed in the Northern Lights video. (Linespeed is up to 100 for HSTs Edinburgh-Aberdeen.)

 

[LRV3004]

Defective AWS when competent person is provided - proceed at normal permissible speed, except during poor visibility when the speed must not exceed 40mph.

Defective AWS when competent person is NOT provided - freight trains and track machines must not exceed 50mph. All other trains must not exceed 60mph. In both of these cases, if the line speed is lower than the lower speed obviously applies. In both cases, the train will proceed to a location where a competent person can be provided.
In the case of poor visibility, the maximum permissible speed is 40mph, whether a competent person is provided or not.

 

[skyhigh]

Though it's also worth noting some operators don't recognise the concept of a 'competent person'. For example the 60/40 mph speed restrictions always apply for us, even if we have 2 qualified drivers who sign the route in the cab.

 

[Dai Corner]

It was in many quarters argued that it was an advisory system, given that if an AWS warning is acknowledged by the driver it takes no further action you can perhaps appreciate this point of view.

Indeed. The clue is in the names
Automatic Warning system
Automatic Train Protection
Train Protection and Warning System

 

[Efini92]

Full isolation of a Mk4 TPWS system would definitely do that. Not sure about the temporary isolation toggle switch.

Temporary isolation switch has no effect on AWS.

60/40(poor visibility)
Isolating AWS will also knock out TPWS on most stock I imagine.
Realistically what should happen is, work to next suitable place to be taken out of service, detrain and return empty to depot.

certainly on the older stock it would, the tpws piggybacked off the AWS.

 

[bramling]

I don't think that applied pre-Southall.

Certainly no "competent" person accompanied the driver in the cab after the AWS failed in the Northern Lights video. (Linespeed is up to 100 for HSTs Edinburgh-Aberdeen.)

In the case of the Video 125 film, it’s highly likely there was already a traction inspector (or equivalent) present as part of the filming.

I suspect nowadays the AWS failing would mean the filming would be terminated, being deemed to pose a risk of distraction in the degraded circumstances.

 

[D365]

Temporary isolation switch has no effect on AWS.

certainly on the older stock it would, the tpws piggybacked off the AWS.

Thanks. On older fitments, the TPWS does indeed "piggyback" off the AWS. On my TPWS Mk4 fitments, the "AWS Isolation" switch is being relabelled to "*Full Isolation", but has the same effect.

 

[Efini92]

Thanks. On older fitments, the TPWS does indeed "piggyback" off the AWS. On my TPWS Mk4 fitments, the "AWS Isolation" switch is being relabelled to "TPWS Isolation", but has the same effect.

Is there not a separate isolation for AWS and TPWS on the MK4?

 

[D365]

Is there not a separate isolation for AWS and TPWS on the MK4?

Oops, of course there is. What I meant to write is that the "AWS Isolation" becomes "Full Isolation", with a new switch installed for AWS only.

 

[hexagon789]

In the case of the Video 125 film, it’s highly likely there was already a traction inspector (or equivalent) present as part of the filming.

I suspect nowadays the AWS failing would mean the filming would be terminated, being deemed to pose a risk of distraction in the degraded circumstances.

 

[ComUtoR]

Oops, of course there is. What I meant to write is that the "AWS Isolation" becomes "Full Isolation", with a new switch installed for AWS only.

I've never seen a retrofit of Mk4. Is the additional AWS isolation a requirement ?

(I drive both old and new)

 

[Efini92]

I've never seen a retrofit of Mk4. Is the additional AWS isolation a requirement ?

(I drive both old and new)

I didn’t think it was retrofitted anywhere.

 

[D365]

I've never seen a retrofit of Mk4. Is the additional AWS isolation a requirement ?

(I drive both old and new)

I didn’t think it was retrofitted anywhere.

I’m not sure about the Network Rail Class 43s, but the majority of ETCS fitments for British locomotives will include Unipart or Thales Mk4. This is in order to standardise the installation designs, as ETCS will need to interface with the TPWS in order to transition into/out of ETCS zones.

 

[Tynwald]

You dont do it

 

[skyhigh]

You dont do it

You don't do what?

 

[43096]

I’m not sure about the Network Rail Class 43s, but the majority of ETCS fitments for British locomotives will include Unipart or Thales Mk4. This is in order to standardise the installation designs, as ETCS will need to interface with the TPWS in order to transition into/out of ETCS zones.

From this (https://www.porterbrook.co.uk/news/class-43-etcs-retrofit-achieves-level-2-testing) it looks like the power cars get a TPWS retrofit as you have described.

 

[Tynwald]

Put a train into service with safety system defetcts TW5

And operators SMS

 

[D365]

From this (https://www.porterbrook.co.uk/news/class-43-etcs-retrofit-achieves-level-2-testing) it looks like the power cars get a TPWS retrofit as you have described.

Thanks for the photo.

Put a train into service with safety system defetcts TW5

And operators SMS

Can you elaborate? This doesn't make sense without context.

 

[Efini92]

Thanks for the photo.


Can you elaborate? This doesn't make sense without context.

@Tynwald is referencing the rule book (tw5) which says trains can’t enter passenger service with defective AWS.
SMS is the TOC specific rules, in this case It would be dealing with an AWS fault in service.

 

[physics34]

@Tynwald is referencing the rule book (tw5) which says trains can’t enter passenger service with defective AWS.
SMS is the TOC specific rules, in this case It would be dealing with an AWS fault in service.

Yes and if it fails 'in service' that will normally mean must detrain at next suitable location.

 

[D365]

@Tynwald is referencing the rule book (tw5) which says trains can’t enter passenger service with defective AWS.
SMS is the TOC specific rules, in this case It would be dealing with an AWS fault in service.

Thank you. I’m still learning my way around the acronyms

 

[Efini92]

Thank you. I’m still learning my way around the acronyms

There should be a degree course in railway terminology

 

[Dai Corner]

There should be a degree course in railway terminology
Not quite the same, but you can do a degree in railway operations

https://www.ciro.org/wp-content/uploads/2021/03/Bachelor-of-Science-Degree-2020.pdf

Bachelor of Science Degree in Railway Operations Management
This two-year course is ideal for anyone who has a Higher National Diploma, Diploma of Higher Education or equivalent work experience that can be considered instead through ‘Recognition of Prior Learning’. You
must also have several years’ experience in the rail industry covering different aspects of railway operations.
This is a work-based learning course that we deliver with our academic partner, Glasgow Caledonian University. It is comprised of 5 modules which are delivered over 6 trimesters. Each module begins with a classroom-based tutorial. You are then assigned a personal tutor for each module who will support, guide
and mentor you through the content.