Differences between TPWS, ATP and ETCS

[D365]

The design requirements to be "ERTMS ready" are laid down and standardised in one of the many European specifications, and would be different from those to be ready for some older ATP system, so the benefit of having a train prepared for the older system is probably limited if it turns out that it needs to be fitted with ERTMS instead. ERTMS also avoids some of the capacity penalties of older ATP systems and is expected to be ultimately upgradeable to Level 3 which offers a significant capacity benefit.

Is this European specification something that has been cascaded down to UK rolling stock?

 

[edwin_m]

Is this European specification something that has been cascaded down to UK rolling stock?

I'm not aware of the details, but I believe this is a standard interface for all suppliers so it would be a bit nonsense for the UK to do something different.

 

[Nym]

I'm not aware of the details, but I believe this is a standard interface for all suppliers so it would be a bit nonsense for the UK to do something different.

Which is exactly why it is what the UK would do.

Bearing in mind that locomotives built almost entirely to European specification, were until recently still required to have (entirely pointless) adaptation devices to make them work with the very European ETCS equipment destined to be fitted.

 

[TVS1049]

Yes, IF the signal if fitted. But under the current design requirements, the vast majority of signals not at junctions are normally not fitted with TPWS.

This always troubles me especially when knowing how many signals are not fitted with TPWS.
AWS has no control over the speed of the train and it allows rear-end collisions like the Loversall Carr Junction crash in Doncaster (RAIB Report 08/2023).

The report actually points out that even if the signal was fitted with TPWS, the collision would have still occurred.
A continuous supervision of speed will be necessary to avoid the accident. Well, it means we need ATP. It can be an intermittent one, it can be ETCS Level 2, it can be a moving block CBTC.

I am disappointed that the risk of rear-end collisions like this is usually dismissed.

 

[43066]

The report actually points out that even if the signal was fitted with TPWS, the collision would have still occurred.
A continuous supervision of speed will be necessary to avoid the accident. Well, it means we need ATP. It can be an intermittent one, it can be ETCS Level 2, it can be a moving block CBTC.

I am disappointed that the risk of rear-end collisions like this is usually dismissed.

When was the last fatality or serious injury caused by a rear-end collision?

 

[najaB]

I am disappointed that the risk of rear-end collisions like this is usually dismissed.

It's not dismissed out of hand. When considering any control you need to balance the cost of implementing it against the product of the likelihood of the risk and the costs/losses that would be incurred if it did.

Rear-end collisions aren't common, and when they do happen they don't result in large losses.

That combination means that the cost of rolling out TPWS to cover all signals vastly outweighs the losses. In the same way that it doesn't make sense to spend £1,000 on a security system to protect a £500 bike.