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Grade Separation?

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AndyPJG

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I can't see any evidence of a dive under on the Hampton Court branch - you can see on the NLS mapping site before and after the flyover was built.

Construction of a fly under would have be very problematic with regards to levels conflict with Claygate Lane and Portsmouth Road.
 
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glbotu

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When grade-separating quad tracks paired by direction, is it ever considered to slew the outer tracks and insert the turnouts in-between? Example an alternate Hitchin could be: DS-turnout-DF // UF-turnout-US, instead of turnout-DS-DF // UF-US-turnout.

That would remove the need for a DF train to cross the DS in order to access the diverging route, and require not much more land take than for an 'outer' turnout. Also, since the slewed outer tracks are likely to be the Slows, it probably wouldn't cause much compromise on linespeeds.

Isn't that how Airport Junction looks (between Hayes and Heathrow)? It's also, I think, the plan for grade separating Werrington Junction (if ever that plan comes to fruition), largely because there's already a handy gap between the Down Fast and the Up Stamford.

Correct me if I'm wrong.
 

NotATrainspott

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Isn't that how Airport Junction looks (between Hayes and Heathrow)? It's also, I think, the plan for grade separating Werrington Junction (if ever that plan comes to fruition), largely because there's already a handy gap between the Down Fast and the Up Stamford.

Correct me if I'm wrong.

Not quite. In any case, Airport Junction is in the process of being made significantly more complicated. rebmcr's arrangement is efficient when tracks are paired by direction, but the GWML is paired by main/relief. The HEx tunnel spur was built with grade-separation off the main lines only, but it will be necessary to have grade-separation onto the reliefs for the 6tph Elizabeth Line service too. IanVisits has had some articles on the works including some interesting diagrams showing the state of the junction after each Xmas blockade.
 

swt_passenger

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Isn't that how Airport Junction looks (between Hayes and Heathrow)?

GW is paired by use, not paired by direction. Following the rebuild, both mains and reliefs have grade separation. From the perspective of the through lines, all the branch connections are on the outside.

An interesting feature of the final layout (Xmas 2016 in the article linked in the above post) is that they will still have some alternative routes as well, e.g. using the crossovers on the branch there are two routes shown from branch to up main, and two routes from down relief to branch, I'm assuming the two airport flyovers are bi-directional.
 
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edwin_m

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Isn't that how Airport Junction looks (between Hayes and Heathrow)? It's also, I think, the plan for grade separating Werrington Junction (if ever that plan comes to fruition), largely because there's already a handy gap between the Down Fast and the Up Stamford.

Correct me if I'm wrong.

The consultation leaflet somebody linked to on another thread showed the diveunder ramping down between the Up and Down Stamfords (the Down Stamford is also the Down Slow). If the Up diveunder track was laid in the gap you mention, then there would have to be two single line ramps which would cost more and take more space than one double line ramp. I presume the Up Stamford will be moved across into the gap at the start of the work, and the ramp excavated in the space it was moved out of.
 

glbotu

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GW is paired by use, not paired by direction. Following the rebuild, both mains and reliefs have grade separation. From the perspective of the through lines, all the branch connections are on the outside.

Of course it is, I'm an idiot.......

It's still a similar idea though, where the flyover starts between tracks, rather than on the "outside"

An interesting feature of the final layout (Xmas 2016 in the article linked in the above post) is that they will still have some alternative routes as well, e.g. using the crossovers on the branch there are two routes shown from branch to up main, and two routes from down relief to branch, I'm assuming the two airport flyovers are bi-directional.

That does look like quite a flexible system, but then they are increasing the service by about 4tph, so I assume it's necessary.
 

Dr_Paul

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The double grade separation at Hampton Court Junction is impressive and in fact it can be easy to forget about the line to/from Oxshott given the flyover taking the Down Hampton Court branch. This is an old diagram that appears to show the Down Hampton Court branch as being a dive-under.

That's a fascinating diagram. Was this the original proposal? The problem with a burrowing junction here is that the main line is up on an embankment; the down line to Hampton Court would either have to cross Claygate Lane and the Portsmouth Road on level crossings, or burrow underneath them, with pretty fearsome grades as a result. Adding to the fun, there is a stream running along the south side of the Portsmouth Road, the Wrythe, which would have to be dealt with in the latter case.

It's possible that the question of level crossings was looked at, and a flying junction was seen as a better option. Maybe the permanent costs of having a signal box at each one were weighed up against the one-off cost of the approach viaducts and the big span over the main line?
 

snowball

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The application for a T&W order for Werrington has gone in:

https://www.thegazette.co.uk/notice/2671521

Network Rail Infrastructure Limited (“Network Rail”) of 1 Eversholt Street, London, NW1 2DN, has applied to the Secretary of State for Transport under section 6 of the Transport and Works Act 1992, for the above-mentioned Order under sections 1 and 5 of that Act.

The draft Order gives statutory authority to Network Rail for the construction, maintenance and operation of a grade separated junction in the form of a dive under beneath the East Coast Main Line (ECML) at Werrington junction. This will remove a key rail bottleneck in the Peterborough area, allowing trains from the Stamford Lines to reach the Great Northern Great Eastern lines without crossing the East Coast Main Line on the level. The scheme will, in combination with other schemes, increase the capacity on the ECML to allow for up to two extra train paths per hour in each direction for long distance high speed trains.

The construction of the new dive under requires works to move the Stamford lines westwards to allow space for the tracks to pass beneath the ECML. The scheduled works include a replacement footbridge at Cock Lane; diversion of Brook Drain and related watercourses; a widened Lincoln Road bridge, a further bridge to carry utility apparatus and a footpath, bridleway and cycle-track over the railway and a new access road for properties on Hurn Road. Temporary bridges over the Marholm Brook and the railway will allow access during construction to the main construction compounds. The Order also authorises further ancillary works including utilities diversions.
 
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