Welwyn viaduct capacity mitigation?

[Backroom_boy]

Bit crayonista, but would putting in platform loops at Welwyn North (demolishing existing structures and building out into the car park) so allowing the throughlines to be unimpeded solve much of the capacity constraints?

 

[30907]

Bit crayonista, but would putting in platform loops at Welwyn North (demolishing existing structures and building out into the car park) so allowing the throughlines to be unimpeded solve much of the capacity constraints?

Essentially no, because any train that stopped there would have to rejoin the main line through the tunnel, so it would still use 2 non-stopping paths AND have an extended stop at Welwyn N (to let a non-stop overtake). You'd have to bore a new tunnel so the loops could go through to Woolmer Green. Or close Welwyn North, not that I dare suggest that

 

[Backroom_boy]

Essentially no, because any train that stopped there would have to rejoin the main line through the tunnel, so it would still use 2 non-stopping paths AND have an extended stop at Welwyn N (to let a non-stop overtake). You'd have to bore a new tunnel so the loops could go through to Woolmer Green. Or close Welwyn North, not that I dare suggest that

Not sure I follow; is there way of dumbing it down for me?

 

[Ianno87]

Not sure I follow; is there way of dumbing it down for me?

Welwyn Viaduct can basically take one fast train every 3 minutes in each direction.

The current Welwyn North station location means that an extra 2 minutes or so needs to be allowed for a stopping train to slow down, stop and restart, so a stopping train consumes just slightly less than the equivalent of two non-stop paths - it's own path, and part of a further path lost by physically being stationary on the main line.

If the platforms were on loops, a stopping train would need to consume on path on arrival into the station, pull into the loop to be overtaken, and then pull back out into the next path that also needs to be empty - i.e. a stopping train takes two paths .

The best way I can think to explain it! (The sinplest bits of train planning are always the wordiest to explain!)

 

[HST43257]

Really the full 4 tracking is needed - Digswell to Woolmer Green AND Holme Jn to Peterborough.

 

[Ianno87]

Really the full 4 tracking is needed - Digswell to Woolmer Green AND Holme Jn to Peterborough.

That is indeed the plan. The two extra tracks concerned are high speed in nature, leave from Euston and run via the outskirts of Birmingham and Derby/Nottingham.

 

[30907]

Welwyn Viaduct can basically take one fast train every 3 minutes in each direction.

The current Welwyn North station location means that an extra 2 minutes or so needs to be allowed for a stopping train to slow down, stop and restart, so a stopping train consumes just slightly less than the equivalent of two non-stop paths - it's own path, and part of a further path lost by physically being stationary on the main line.

If the platforms were on loops, a stopping train would need to consume on path on arrival into the station, pull into the loop to be overtaken, and then pull back out into the next path that also needs to be empty - i.e. a stopping train takes two paths .

The best way I can think to explain it! (The sinplest bits of train planning are always the wordiest to explain!)

Thanks, hope that explains it better than I did!

 

[swt_passenger]

That is indeed the plan. The two extra tracks concerned are high speed in nature, leave from Euston and run via the outskirts of Birmingham and Derby/Nottingham.

I saw what you did there...

 

[adamedwards]

My suggestion is move the station south of the viaduct with a glass footbridge along one side of the viaduct. Glass floor to the bridge and it would be a tourist attraction.

 

[Ianno87]

My suggestion is move the station south of the viaduct with a glass footbridge along one side of the viaduct. Glass floor to the bridge and it would be a tourist attraction.

That is, what, best part of a mile? It'd be within touching distance of Welwyn Garden City and render the station so pointless that you may as well close it!

 

[Bald Rick]

That is, what, best part of a mile? It'd be within touching distance of Welwyn Garden City and render the station so pointless that you may as well close it!

I assumed it was said in jest!

 

[A0]

Really the full 4 tracking is needed - Digswell to Woolmer Green AND Holme Jn to Peterborough.

The latter one of those is probably not too difficult in the scheme of things.

Digswell - Woolmer Green is a nightmare. Hindsight being the helpful thing it is, it probably would have been easier if the GNR at Hatfield had followed the route of the Great North Road - then with a bit of careful siting, their station could have been called Welwyn North and actually been accurately named into the bargain, since Welwyn North is neither in Welwyn nor north of Welwyn Village.

 

[furnessvale]

That is indeed the plan. The two extra tracks concerned are high speed in nature, leave from Euston and run via the outskirts of Birmingham and Derby/Nottingham.

Stop upsetting the antiHS2 brigade. You know full well that HS2 is ONLY to knock 20 minutes off the jouney time to Birmingham for a handful of business men going to meetings who should be video conferencing in the first place!

 

[hwl]

There are 4 capacity issues around the viaduct area:
a) 2 tracks over the viaduct
b) double block section over the viaduct to stop any slam door stock without central locking doors from stopping there (any passengers doing a Wylie E Coyote walk)
c) 2 tracks through the station
d) 2 tracks through the tunnel

Everyone seem to forget about b) which will get sorted with resignalling.
After that addressing 2 tracking through the tunnel and station would substantially reduce the remaining viaduct issues.

 

[A0]

There are 4 capacity issues around the viaduct area:
a) 2 tracks over the viaduct
b) double block section over the viaduct to stop any slam door stock without central locking doors from stopping there (any passengers doing a Wylie E Coyote walk)
c) 2 tracks through the station
d) 2 tracks through the tunnel

Everyone seem to forget about b) which will get sorted with resignalling.
After that addressing 2 tracking through the tunnel and station would substantially reduce the remaining viaduct issues.

I had wondered whether simply 4 tracking from Welwyn North station northwards on its own would be sufficient - leaving the viaduct as 2 track. Still won't be cheap though as it would wipe out at least a dozen houses in Cob Lane Close and Warren Way - call it an average house price of £ 700k and you're probably not far off - and that's if you go on the west side - if you did it on the east side, you'd be looking at some even more expensive houses. That's before you add the cost of building 2 new tunnels.