Rail safety improvements over the past 10 years

[Railsigns]

ATP was then, as now, only fitted to GWML and Chiltern

The Cambrian Lines also have ATP, as part of ETCS Level 2.

 

[QueensCurve]

So in other words politics stopped it from happening sooner and less politics might have saved lives. Or is that an unfair thing to say. I'm an outsider.

I think the politics were significant.

It was the Hidden Report (Clapham Junction) That recommended BR trial ATP. This they did on the GWR and Chiltern routes. As noted, these are incompatible systems.

ATP is difficult to overlay on existing signalling systems without adversely affecting train performance. This is particularly true on a mixed traffic railway where different trains have different stopping distances. The potential is that lighter, more stoppable, trains are stopped prematurely. Conversely, heavy trains with a long stopping distance might still overrun. It is also expensive.

Controversially BR used a cost-benefit analysis to show that ATP should not be used nationally.

This was where BR started the development of TPWS. As originally conceived, it is a system that uses a sort of best case analysis to stop any train which will overrun a danger signal without guaranteeing that it will always prevent the SPAD or any subsequent collision.

After the Ladbroke Grove disaster (following on from the fatal collision at Southall 2y earlier). the political pressure for ATP became unmistakable. Then Transport Secretary John Prescott said he didn't care how much it cost, the railways had to be absolutely safe.

Eventually it was agreed that TPWS would become the national system and it was rolled out.

I trust someone will put me right if any of the above is inaccurate.

 

[thenorthern]

Looking at the report into the Smiler Crash at Alton Towers one thing that is mentioned that staff began to ignore safety warnings as most of them were false alarms and that staff weren't trained well enough to operate the ride and because of these failings Alton Towers had to pay the price yesterday at Stafford Crown Court when they were fines £5 million.

Similar things happened in rail accidents such as at Southall it wasn't considered serious not to run a train with defective AWS and Great Western Railway were fined £1.5 million. Also with the Ladbroke Grove crash where it was shows the Thames Trains training was ineffective and the company was fined £2 million.

These tragic incidents has in effect told the railway companies not to be negligent on safety in any situation.

 

[najaB]

With this discussion ongoing it's interesting that the USA has missed the initial deadline for fitment of Positive Train Control. And in the BBC article on the train accident in New Jersey they say "While the US sees its fair share of deadly freight train crashes and derailments, this is the first deadly passenger train crash for five months." - where in the UK it's been over eight years.

 

[DerekC]

ATP is difficult to overlay on existing signalling systems without adversely affecting train performance. This is particularly true on a mixed traffic railway where different trains have different stopping distances. The potential is that lighter, more stoppable, trains are stopped prematurely. Conversely, heavy trains with a long stopping distance might still overrun. It is also expensive.

ATP is certainly expensive, but the discussion of the impact of train performance is inaccurate. In a modern system the ATP onboard computer is programmed with the brake rate its train can achieve, and can therefore apply the brakes sooner (if it's a freight train) or later (if it's a modern EMU) - for example.

This was where BR started the development of TPWS. As originally conceived, it is a system that uses a sort of best case analysis to stop any train which will overrun a danger signal without guaranteeing that it will always prevent the SPAD or any subsequent collision.

TPWS is very simple. It has a speed trap on the approach to the signal and a train stop at the signal. It has different timer settings in the onboard kit for freight and passenger, so that the speed trap will operate at a lower speed for freight. It will stop most SPADs within the overlap. RSSB figures suggest it has about 90% of the effectiveness of full ATP at a small fraction of the cost so it was undoubtedly a good buy. Its design hasn't changed since its inception - the only improvement (being rolled out very slowly now) is in the driver's controls, but it doesn't make any difference to how it works.

 

[QueensCurve]

ATP is certainly expensive, but the discussion of the impact of train performance is inaccurate. In a modern system the ATP onboard computer is programmed with the brake rate its train can achieve, and can therefore apply the brakes sooner (if it's a freight train) or later (if it's a modern EMU) - for example.

No doubt that is now true, but was it so in the 1990s?

 

[E16 Cyclist]

A big disadvantage of ATP is that its not a continuous system, by this i mean should you receive a single yellow and the single ahead clears from a red to a less restrictive aspect then should you take power the onboard computer will think you are still approaching a red signal and apply the brake, the way they got round this was to introduce release speeds which is a maximum speed you can approach the signal at which is why you may see a train crawl up to a green signal and because of release speeds ATP was never designed to prevent a SPAD instead it was always designed to stop you in the overlap.

TPWS is very effective at what it does but the drawback is unlike ATP it doesn't talk to the driver, by talk i mean if you overspeed or going too fast towards a red it was warble at you first giving you a chance to do something about it whereas TPWS will just dump the brake on you and the driver could possibly be at a loss as to why, this is getting better with the release of TPWS version 4 which while not providing a warning does at least tell the driver why the brakes have applied thereby removing one of the main reasons for 'reset and continue' which kinda defeated the purpose of having it

 

[Phil.]

I have a vague memory of TPWS introduction on the MML being one of the first. Wasn't there talk of it being a poor alternative to ATP, including only being effective below 75mph?

Yup. It was introduced as a knee jerk reaction and much tabloid hysteria.

 

[QueensCurve]

Yup. It was introduced as a knee jerk reaction and much tabloid hysteria.

The hysteria to provide ATP or at least that something must be done. TPWS was the something that was done.