O L Leigh
Established Member
I was wondering whether any of the wise heads on this forum could explain to me why it is that, in the era of TPWS, there are still stations that appear to use double-blocking. Two that come most readily to mind are Cambridge (where you cannot access P4 on the Down if there is a movement signalled in or out of P5/6) and Newport Wales (where you cannot access either P3 or P4 if there is another train on the opposing platform with the route set out of the platform).
Now I understand that you want to protect the point of conflict in the event that a driver makes a total horlicks of stopping and SPADs the signal, but as signals at these locations are equipped with TPWS anyway the chances of a SPAD resulting in a collision is low. This also contrasts with junctions such as Proof House where you similarly have points of conflict where a train passing a signal could potentially cause a collision but where double-blocking is not used.
It's quite irritating to be sat at a red signal looking at your vacant platform but knowing that you can't access it until after another train has finished using some other piece of track somewhere near to the bit that you're about to occupy. Obviously it causes capacity constraints and means that it is not possible to fully utilise all the available platform space which can introduce/exacerbate delays. To this humble driver's eyes, it's a daft idea that causes more problems than it solves. So what is it that I'm missing? What salient factor can explain why double-blocking is persisted with?
Now I understand that you want to protect the point of conflict in the event that a driver makes a total horlicks of stopping and SPADs the signal, but as signals at these locations are equipped with TPWS anyway the chances of a SPAD resulting in a collision is low. This also contrasts with junctions such as Proof House where you similarly have points of conflict where a train passing a signal could potentially cause a collision but where double-blocking is not used.
It's quite irritating to be sat at a red signal looking at your vacant platform but knowing that you can't access it until after another train has finished using some other piece of track somewhere near to the bit that you're about to occupy. Obviously it causes capacity constraints and means that it is not possible to fully utilise all the available platform space which can introduce/exacerbate delays. To this humble driver's eyes, it's a daft idea that causes more problems than it solves. So what is it that I'm missing? What salient factor can explain why double-blocking is persisted with?