Grade Separation?

Status
Not open for further replies.

Lewis

Member
Joined
3 Dec 2011
Messages
17
Location
Didcot
In the latest issue of RAIL in the report on Faster Freight it lists 2 options on the Didcot/Oxford section either 4 tracking or Grade Separation.
What is Grade Separation please?
 
Sponsor Post - registered members do not see these adverts; click here to register, or click here to log in
R

RailUK Forums

yorkie

Forum Staff
Staff Member
Administrator
Joined
6 Jun 2005
Messages
55,278
Location
Yorkshire
Crossing at separate grades (using either a flyover, diveunder, or both!), ie. not on the level, and therefore avoiding conflicting movements.
 

WatcherZero

Established Member
Joined
25 Feb 2010
Messages
9,603
Think motorway junctions. Traffic can pass over/under, even turn back on itself without the need of traffic lights.
 

najaB

Veteran Member
Joined
28 Aug 2011
Messages
24,845
Location
Scotland
What is Grade Separation please?
An at grade junction can involve movements that conflict - in other words trains have to cross tracks used by trains travelling in the opposite direction.


This is both a capacity constraint as conflicting moves have to be timed with a sufficient margin, and also a potential safety issue. In the picture above, trains on the green line taking the diverging route conflict with trains on the yellow line.

By using a flyover/diveunder they can remove this conflict.


Trains taking the diverging route no longer conflict which removes both the potential for collision and the timetabling restriction.

(Images from Wikipedia: Flying Junction, double junction)
 

Muzer

Established Member
Joined
3 Feb 2012
Messages
2,755

This is both a capacity constraint as conflicting moves have to be timed with a sufficient margin, and also a potential safety issue. In the picture above, trains on the green line taking the diverging route conflict with trains on the yellow line.

Only a very minor safety issue. That's what signals are for after all!
 

Nippy

Member
Joined
13 Aug 2013
Messages
548
Yes, but if they don't stop they could conflict. Didcot North a few years back an HST passed the signal on the avoider and came to stand on the crossover just after a turbo had cleared the junction on the up.
 

YorkshireBear

Established Member
Joined
23 Jul 2010
Messages
8,102
Only a very minor safety issue. That's what signals are for after all!

Removing a diamond could be considered a safety improvement or a reduction in overall amount of switches etc. Quite a few track related derailments are on S&C.
 

route:oxford

Established Member
Joined
1 Nov 2008
Messages
4,949
In the latest issue of RAIL in the report on Faster Freight it lists 2 options on the Didcot/Oxford section either 4 tracking or Grade Separation.
What is Grade Separation please?

There is already a campaign against in the North Oxford area...

I'm forbidden from saying anything about the campaigners on here myself, but I have found a quote from Hugh Jaeger at Rail Future, Thames Valley from January 2015:-

Network Rail proposes not only enlarging Oxford station but also increasing the line between Didcot and Oxford to four tracks and building flyovers at two junctions, one each at Didcot and Wolvercote. This should future-proof the line until the 2040s.

But in November three Wolvercote Lib Dem councillors declared: “We were horrified to hear of the flyover plans and trust they will be dropped without delay”. Now Jean Fooks has repeated her attack and added that she backs Network Rail’s plans in every ward except her own! And Mike Gotch attacks rail electrification north of Oxford because he dislikes its appearance.
 

Shaw S Hunter

Established Member
Joined
21 Apr 2016
Messages
2,345
Location
Sunny South Lancs
Grade separated junctions are much more widely used on the European mainland than in this country and they do indeed provide significant capacity benefits in congested areas. In the Netherlands back in the 1970s they were a new idea adopted during construction of the Zoetermeer Stadslijn and the then new Schipol route. Since then the Dutch have upgraded many existing junctions with grade separation.

Meanwhile in this country Network Rail seems to be stalling on making firm plans for the urgently needed grade separation of Woking Junction and missed a trick in not providing similar at Ordsall Lane Junction when they had the chance. You will guess that I'm very much in favour of the concept!
 

LNW-GW Joint

Veteran Member
Joined
22 Feb 2011
Messages
16,048
Location
Mold, Clwyd
Didcot comes up as a key future flyover location.
Ordsall Chord should be, but there is no space - so flat junctions.
Bletchley was one of the abortive ones (which should be coming back with E-W Rail).
The freight lines through Crewe ("Independent Lines") are a long-standing example.
 

jopsuk

Veteran Member
Joined
13 May 2008
Messages
12,635
Darlington. Though there's really three that would be useful here- could be combined structures.
1 to the south to bring the Tees Valley line under the mainline to the station side
2 just south of the station to take the Down mainline over or under the Up station line
3 just north of the station, for the same purpose
 

Ianno87

Veteran Member
Joined
3 May 2015
Messages
14,678
Darlington. Though there's really three that would be useful here- could be combined structures.
1 to the south to bring the Tees Valley line under the mainline to the station side
2 just south of the station to take the Down mainline over or under the Up station line
3 just north of the station, for the same purpose

How many trains use the station avoiding line these days? For passenger trains, I thought it was down to the morning Flying Adonis only (0540 ex-Edinburgh) these days. Unless there was a significant quantity of of freight traffic (I.e. several paths per hour) grade separation wouldn't have much purpose.
 

NSE

Established Member
Joined
3 Mar 2010
Messages
1,340
I remember the first trip I took down the SWML beyond my usual limit of Raynes Park. With grade separation at Raynes Park, New Malden, the two at Surbiton, Weybridge, the Alton line and Basingstoke. Seven between Wimbledon and Basingstoke isn't bad going.
 

route:oxford

Established Member
Joined
1 Nov 2008
Messages
4,949
Greenhill.

Which part of Greenhill?

I'm guessing coming from Croy going towards Falkirk High.

There is also potential for the semi-built juncion at Castlecary that wasn't completed during WW2 - which would allow for the singling of the route between Castlecary and Greenhill.
 

3141

Established Member
Joined
1 Apr 2012
Messages
1,609
Location
Whitchurch, Hampshire
I remember the first trip I took down the SWML beyond my usual limit of Raynes Park. With grade separation at Raynes Park, New Malden, the two at Surbiton, Weybridge, the Alton line and Basingstoke. Seven between Wimbledon and Basingstoke isn't bad going.

I take it that by "Basingstoke" you mean Worting Junction, two miles further on.
 

Class 170101

Established Member
Joined
1 Mar 2014
Messages
6,870
Yes, but if they don't stop they could conflict. Didcot North a few years back an HST passed the signal on the avoider and came to stand on the crossover just after a turbo had cleared the junction on the up.

How about our friends from West Coast Railways as a more recent example?

Aynho, Worting, Cogload. Reading

Already done (I think)

Greenhill.

Should be done now as part of E&G upgrade however passive provision has been made.
 

Rick1984

Member
Joined
23 Aug 2012
Messages
891
I often thought some not the mainline junctions in this country obscene, such as the single lead junction from Dumfries onto the WCML, or Carstairs.
 

Senex

Established Member
Joined
1 Apr 2014
Messages
2,542
Location
York
I often thought some not the mainline junctions in this country obscene, such as the single lead junction from Dumfries onto the WCML, or Carstairs.
The scandal of Carstairs is that the clear alignment of the original Edinburgh line from Float Jn is still there, just begging to be rebuilt and brought back into use.
 

Helvellyn

Established Member
Joined
28 Aug 2009
Messages
1,692
Following the success of Norton Bridge, Acton and London Bridge - Network Rail are consulting on Werrington, just north of Peterborough linking the GNML and the GN&GE.

https://www.networkrail.co.uk/east-coast-main-line/werrington-junction/

Which other key junctions need grade segregation?
Aynho, Worting, Cogload. Reading
Pedant mode on but Worting Junction is an at grade junction between the Up lines from Southampton and Salisbury that become the Up Slow and Up Fast respectively and the Down Slow and Down Fast where they become the separate Down Lines to Southampton and Salisbury respectively. The grade separation is where the Up Line from Southampton crosses the lines to/from Salisbury and is known as Battledown Flyover.

Diagram here.

I remember the first trip I took down the SWML beyond my usual limit of Raynes Park. With grade separation at Raynes Park, New Malden, the two at Surbiton, Weybridge, the Alton line and Basingstoke. Seven between Wimbledon and Basingstoke isn't bad going.
If you include the flyover adjacent to Wimbledon Park Depot (specifcially the old Durnsford Road site) then it is eight between Clapham Junction and Worting Junction.

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.

The Weybridge one is actually know as the Byfleet Curve (Diveunder on the Down from Addlestone that joins the Down Slow Line immediately before West Byfleet station. This is an old diagram where the station was still known as West Weybridge. I wonder why at Weybridge the junction was never grade separated coming off the Down Slow heading towards Addlestone?

The Alton line joins the Up Slow line using a flyover to cross the SWML at Pirbright Junction.

The glaring one that never got built by the Southern was at Woking Junction to carry the Up Line from Portsmouth over the SWML towards Basingstoke. The Southern even had the land reserved and it was eventually sold off by BR for housing.

Network Rail want to revive a scheme at Woking, along with grade separation at Basingstoke for the Down Line from Reading to eliminate the at grade Great Western Junction where the Up Lines have to be crossed for both passenger and freight trains coming from Reading.
 

Ianno87

Veteran Member
Joined
3 May 2015
Messages
14,678
How about our friends from West Coast Railways as a more recent example?



Already done (I think)



Should be done now as part of E&G upgrade however passive provision has been made.

Wasn't it the case that in the Wooton Bassett incident the kettle was following behind the HST in the same direction towards Swindon? If so, that conflict wouldn't have been avoided by a grade separated junction.

However, the accident report into the August 1996 Watford Junction accident makes for an interesting read (a head on collision on a flat crossover resulting from a SPAD, with the specific design of the signalling and speed profile being one of the contributory factors).
 

edwin_m

Veteran Member
Joined
21 Apr 2013
Messages
21,567
Location
Nottingham
Darlington. Though there's really three that would be useful here- could be combined structures.
1 to the south to bring the Tees Valley line under the mainline to the station side
2 just south of the station to take the Down mainline over or under the Up station line
3 just north of the station, for the same purpose

If anything is done at Darlington it will most likely be constructing at least one long platform to the east of the through lines with a couple of bays alongside it, an independent track from the bays to the junction and a footbridge over to the train shed. That way Down main line trains still use the shed, Up ones use the new platform and nothing conflicts with anything except the through Bishop Auckland services.
--- old post above --- --- new post below ---
How many trains use the station avoiding line these days? For passenger trains, I thought it was down to the morning Flying Adonis only (0540 ex-Edinburgh) these days. Unless there was a significant quantity of of freight traffic (I.e. several paths per hour) grade separation wouldn't have much purpose.

Very few do today, but both VTEC and First plan to have extra fast Edinburgh-London services.
 
Status
Not open for further replies.

Top