Greater Anglia Crossover Near Ilford

[DynamicSpirit]

Just west of Ilford station, there's a grade separated crossover, where the fast lines swap from being North of the slow lines to being South of them (if you're heading out of London). It occurred to me to wonder what the original point of doing that was... It can't have been cheap to build, and there doesn't seem to be an obvious advantage to swapping the lines over. So why would it have been built that way?

Of the top of my head, the only other example I can think of of a similar bridge that swaps lines over is on SWR just North of Wimbledon: But that one has an obvious purpose: It changes the lines from separated-by use (more useful at the Waterloo terminus) to separated-by-direction (more useful for dealing with the various junctions south of Wimbledon). The one near Ilford doesn't do that, which begs the question, what is the purpose of swapping the lines?

(You also have the swap on the WCML just between Stonebridge Park and Wembley Central, where the DC lines go from one side of the fast lines to the other, but that seems to be associated with the different sets of lines taking different routes, so seems more easily explainable.)

 

[Railperf]

Ilford Flyover

www.gersociety.org.uk

 

[dosxuk]

From Wikipedia:

In the 1930s, a flyover was constructed just west of Ilford to switch the main and electric lines over, to enable main line trains to utilise Liverpool Street's longer west side platforms without having to cross east side suburban traffic in the station throat. The new arrangement also facilitated cross-platform interchange with the Central line at Stratford, with services commencing in 1946. Either side of the Ilford flyover there are single-track connections between each pair of lines, with the westbound track extending to Manor Park and just beyond. The eastbound track extends as far as Ilford station. It was also envisaged that a flyover would be built at the country-end of the carriage sidings at Gidea Park to allow trains bound for the Southend line to change from the main line to the electric line, instead of at the London-end of Shenfield as they do now.

 

[swt_passenger]

Just west of Ilford station, there's a grade separated crossover, where the fast lines swap from being North of the slow lines to being South of them (if you're heading out of London). It occurred to me to wonder what the original point of doing that was... It can't have been cheap to build, and there doesn't seem to be an obvious advantage to swapping the lines over. So why would it have been built that way?

Of the top of my head, the only other example I can think of of a similar bridge that swaps lines over is on SWR just North of Wimbledon: But that one has an obvious purpose: It changes the lines from separated-by use (more useful at the Waterloo terminus) to separated-by-direction (more useful for dealing with the various junctions south of Wimbledon). The one near Ilford doesn't do that, which begs the question, what is the purpose of swapping the lines?

(You also have the swap on the WCML just between Stonebridge Park and Wembley Central, where the DC lines go from one side of the fast lines to the other, but that seems to be associated with the different sets of lines taking different routes, so seems more easily explainable.)

It was all about the expansion of Liverpool St. All the newer suburban platforms 11-18 were effectively on the wrong (east) side with respect to the incoming four tracks from Stratford, so the two pairs (known as through and local) were swapped over to leave the present day “mains” heading into the longer platforms, now in the middle, and the locals now known as “electrics” having a direct route into the east side of Liverpool St.

Then it also presumably fitted in with the design for the cross platform interchange with the LU Central line at Stratford.

(btw there’s another obvious London terminus with a flyover to change from paired by direction to paired by use, namely Kings Cross. But that was converted from its previous purpose - which was to switch the up goods to the west side to access the goods yard, and it’s possibly not so noticeable being much closer to the terminus and approach tunnels.)

 

[Magdalia]

It was all about the expansion of Liverpool St.

It was only partly about Liverpool Street. As you hint, it was also about Stratford.

The Liverpool Street-Shenfield electrification proceeded concurrently with the extension of the Central Line eastwards from Liverpool Street, taking over the Epping/Ongar and Chigwell/Fairlop lines from the LNER.

Then it also presumably fitted in with the design for the cross platform interchange with the LU Central line at Stratford.

The cross platform interchange at Stratford between the Liverpool Street-Shenfield electric trains and the extended Central Line was a key feature of the project.

But it is about Ilford too. Once beyond Stratford the Electric Lines needed to cross over the Main Lines because the Ilford EMU depot is on the north side of the line.

(btw there’s another obvious London terminus with a flyover to change from paired by direction to paired by use, namely Kings Cross. But that was converted from its previous purpose - which was to switch the up goods to the west side to access the goods yard.)

The Holloway flyover was repurposed for passenger use as part of the GN electrification scheme in the 1970s.

And the Bermondsey flyover now does this between London Bridge and New Cross Gate.