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ATP and all that!    
Sir David Davies' Report on Train protection         

ATP and all that!
Sir David Davies' Report on Train protection
19 Mar 2000
by Ray State

what is required is a solution which provides a stepping stone on the route to the final solution to SPADS

Sir David Davies
Sir David Davies is the President of the Royal Academy of Engineering

Hidden Dangers
Hidden Dangers
by Stanley Hall

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Comment on ATP and all that

Signal SN109
Driver's eye view of signal SN109

Safety First means TPWS then ATP says Sir David Davies

At the end of February Sir David Davies published his report on the review of signals passed at danger (SPAD) incidents and the safety systems which could reduce their occurrence.

His findings offer little comfort to the beleaguered railway companies. In particular the report criticises the concentration on the arguments between ATP and TPWS which is taking the emphasis off the ultimate goal of installing the European Train Control System (ETCS).

This technology being tested in Europe can operate with sufficient reliability as to make lineside signalling redundant. In light of the questions over the visibility of signals such as SN109 and others involved in the Southall accident it could be concluded that this is a step in the right direction. But as Sir David points out, if ETCS is the ultimate goal, then a short term solution is required to bridge the gap before it is available in the UK. What is required is a solution which provides a stepping stone on the route to the final solution to SPADS.

With this in mind the report concludes that TPWS is the best short term solution both from a timescale and effectiveness point of view. The basis of this is the fact that TPWS was already being proposed at the time of the Ladbroke Grove collision and the programme has already been submitted to the HSE.

Recognising the shortcomings of TPWS at speeds over 70mph, Sir David suggests a variant known as TPWS+ could be employed which would operate successfully up to 100mph. This would cost in the region of £70m on top of the estimated cost of TPWS alone of £193m.

A second suggestion has been made which may be attractive if the ultimate goal is ETCS. This is TPWS-E and uses passive transponders (Eurobalise) in the track to control line speed. This is on the road to full ETCS and is considered to have the same benefits as TPWS+.

ETCS in Europe is proposed to be introduced in three phases designated levels 1 to 3. In level 1 the existing signalling is retained while the balise in the track transmits to the train the line speed and signal aspect and permits the train to compute the distance to stop. In level 2 the signals are dispensed with but fixed block sections are retained. In level 3 fixed block is replaced by full moving block in which a safe distance is continuously maintained behind the train in front consistent with its speed.

It remains to be seen as how the industry will respond to this report.

The report echoes the appeal made in Professor Uff's Southall Report for co-operation between rail companies in safety research. Recognising that the fragmented industry has to difficulty in funding its own research Sir David suggests that the subject may fall within the scope of the Strategic Rail Authority.

Whilst this report is being studied it is worth raising one's eyes to the activities on the other side of the Atlantic. There the highly mechanised track maintenance activity applying to most US Railroads and the distances from suitable power sources means that balise operation is not favoured. Railtrack too must be viewing multiple balise installation with concern.

In the US the focus of research has been in Communication Based Train Control (CBTC) which is largely balise-free. The problems in developing this concept are immense but so are the benefits particularly in "dark territory" – the areas where no signalling or train position recording exists. The recently announced Illinois Department of Transportation (IDOT) project (see Danger Ahead! 11 Feb 2000 - Positive Train Control RFP Released ) is a large scale project equal to ETCS in Europe and has the same objectives. The main difference is that it is quantum leap beyond ETCS if it can be made to work.

Thinking railmen are asking themselves whether the length of time that Europe has taken to develop ETCS means that it is about to be made obsolete by US designed CBTC technology which offers lower first cost and greater flexibility without the on-going track maintenance problems.

This issue will not be lost on the US companies intending to participate in the IDOT project.

Following the severe railway accident at Ladbroke Grove Junction near Paddington on 5 October 1999, the Deputy Prime Minister asked Sir David Davies to undertake an independent review of possible forms of Automatic Train Protection suitable for fitting on the national rail network and associated rolling stock to achieve improvements in railway safety and protection from signals passed at danger. Automatic Train Protection for the Railway Network in Britain: a Study is Sir Davidís report, published 22 February 2000.

Safety First means TPWS then ATP says Sir David Davies
22 Feb 2000
HSE publishes details of rail signals passed at danger
27 Jan 2000
Positive Train Control RFP Released
11 Feb 2000

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