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.What is Grade Separation please?
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!
The WCML Norton Bridge project is a good example which is explained above.
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?
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 Rails plans in every ward except her own! And Mike Gotch attacks rail electrification north of Oxford because he dislikes its appearance.
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?
How about Euxton Junction, to keep Chorley line traffic away from the WCML fasts?Which other key junctions need grade segregation?
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
Greenhill.
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.
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.
Aynho, Worting, Cogload. Reading
Greenhill.
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.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.
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.Aynho, Worting, Cogload. ReadingFollowing 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?
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.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.
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.
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.