Im surmising this is another example where the driver has a green aspect with the junction indicator alight but the actual point of divergence some distance away. It would seem more appropriate to have a restricted aspect in these cases and only step up the signal beyond the point of divergence once the train was actually detected on the points. The other aspect here is acceleration rate of modern trains is significantly above what had been built by BR.
Faster turnouts cost more but also take up a lot more space, the length from switch to crossing being approximately proportional to the turnout speed. I think some of the turnouts at Spital Junction (site of the two previous similar incidents) are planned to have their speeds increased when next due for renewal, but this isn't always possible everywhere.
The fundamental problem is that while "speed" is a "simple parameter" for a safety system installed in a train cab "location and signal state" are very much not.
Money is a fairly important factor.
The Slow to Highdyke Junction is 40mph. I’m not sure whether this changes at the junction itself.
The slow to fast at Highdyke Jn. is 40mph I checked with the appendix. As the slow is only 40mph and he took the 25mph points doing 55mph looked like the driver forgot he was to go on the slow.
TPWS is very difficult to implement for anything other than just plain signals at Danger. It's an unfortunate side effect of how it was designed to be cheap and the fact that it's a 'dumb' system, i.e there is no computer in the cab actually giving the driver real time information in advance, e.g PZB. For these sorts of low speed approaches, it is technically possible to release the signal from Danger later than usual and place the OSS loops closer together but it's difficult to time everything correctly.
TPWS is not as good as full ATP, but ATP is also quite expensive. Surely a pair of TWPS grids which are set to be energised when a diverging route is set can't be that difficult to implement?
Surely you could have 2 sets of grids, with the second set much closer to the crossover and set for the lower speed, such that if you have a driver who accelerates, they get caught by the 2nd OSS and the brakes get applied? At least they'll be at a much lower speed less likely to fling luggage and laptops from overhead racks onto skulls etc.
Would it be possible to have 2 sets of loops in this case? I seem to recall that quite a few signals have 2 sets of OSS loops, including rather infamously the signal that Tangmere passed about 10 years ago.
At that point you're increasing the complexity to the point where you may as well have just installed any flavour of ATP. TPWS was primarily intended to reduce risk approaching conflicts, and was designed to be simple. For this scenario we're now looking at: 1 set of loops for the main route, 1 set of loops for the diverging route when passing Grantham, and 1 set of loops for the diverging route when stopped at Grantham. Arguably these work as layers, so you wouldn't need to switch off the higher-speed loops if the lowest speed route is set, but you'd still need some form of connection to detect the signals and stopping/non-stopping controls.
Yes, but then you'd have two OSSs that are either ineffective at protecting accelerating trains or could interfere with decelerating trains. More TPWS isn't a practicable solution.
That's part of the problem, both here and at Peterborough. The signalling was designed when such speeds would not be achievable at the critical point from the standing or rolling start at the previous signal. Modern trains, whether Arterios or Azumas, may have their shortcomings, but their acceleration is phenomenal.
That was my suggestion above hold the first loop signal at red until the train activates the the track circuit on the diverging points. However, there is still a risk of forgetting as the point of divergence is so far away from the signal and also a risk you can sight the next main running signal and see its at a green and get false assurance? No solution is elegant like the SPAD signals introduced after Cowden but are a simple fix in advance of resignalling with ETCS.
An 801 can reach 60mph in 2140 feet, so well under half a mile
Once you start introducing that level of control off the main line, the train diverging off will be at a crawl - likely impeding the train behind - which will start to see adverse signals - defeating the object of diverting it out of the way. In that case might it be better to keep the train in front on the main line and diverge off at a better place such as the SL after the tunnel.
This is considered at complex locations but has to be balanced against restricting the capacity of the railway.
Being moved into the ROC does not automatically meant ETCS will be fitted.
Indeed, although if ETCS L2 is fitted even as an overlay, ETCS fitted train could use it, which in this location will include all stock heading south of Peterborough, i.e.those most at risk of this kind of incident.
Thanks. I'm not that technically minded with these newer trains.
True!
