Yes, will be interesting to see the recommendations. However with ETCS imminent for the ECML, the level of incidence of this type of problem and the difficulty in having a switchable by route TPWS, I don't anticipate major changes.
Separately I just want to register my constant amazement at the feat of engineering design that TPWS is. Using nothing but the most simple equipment and most basic principles of physics, they designs a system for effectively tuppence that can bring a 125mph train safely to a stand.
In principle it ought to be possible to trigger different TPWS loops at the approach to a junction depending on the route set. This information is readily available in the interlocking but would need to be passed to the loops via a new control to the trackside. I assume this didn't happen at Peterborough because of the difficulty in modifying a 1970s-era relay interlocking, but does anyone know if it is done on newer signalling schemes elsewhere?
I was involved in the early days of TPWS circa 1994, when some colleagues analysed the accident reports back to around 1968 to assess whether the accident would have been less severe, or would not have happened at all, if a TPWS-like system had been fitted at the time. This also allowed for the fact that the older rolling stock involved in many of these accidents would now be replaced by newer and more survivable designs. The conclusion was that TPWS would avert about 70% of the casualties that an ATP system would, which was noted with some skepticism by Uff-Cullen but borne out some years later in an analysis by Stanley Hall in Modern Railways magazine. TPWS+ has probably improved this further since then. Even then the predicted cost was near the maximum that the expected casualty reduction would justify, and the cost later increased due to measures such as proving the system operational.
I'd put the track circuit above TPWS, personally. TPWS is great for what it is, but it does leave some important problems - it cannot cope with different speeds on diverging routes, it cannot adjust to different speed profiles, and it provides no advance warning before tripping the brakes. I also have it in the back of my mind that it's not fail-safe, as the grids require power to activate.
I'd probably agree with you on the track circuit, although the number of accidents in absolute block areas with limited track circuiting may make track circuit
block a better candidate.
The lack of failsafe was known and agreed at the time by senior people in BR and Railtrack (who unlike some of their successors actually had both technical knowledge and influence within the organisation). To cause a SPAD-related accident it is necessary for the TPWS to fail but also for some other event to occur such as the driver misinterpreting the signal or braking too late. Both of these should be very unusual circumstances so the chance of both at the same time is infinitesimal - provided TPWS failures are promptly identified and remedied so they don't remain as latent faults. It's worth noting that a modern safety integrity analysis wouldn't consider AWS to be failsafe either.
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