Underground track swap

[TRAX]

Hello all

Just a little curious question, in several places on the LUL network the tracks swap from left to right and vice-versa. For example between Oxford Circus and Highbury & Islington on the Victoria Line, or between Elephant & Castle and Moorgate on the Northern Line. Why is that ?



Thanks !

 

[transmanche]

If you look at Euston on that map, it becomes clearer. In order for the Victoria line and Northern line City branch to have a northbound-northbound and southbound-southbound cross-platform interchange at Euston, one direction of the Victoria line needed to 'roll over' the other. There just isn't room between Kings Cross St Pancras and Euston to do this, so it happens between Highbury & Islington and Kings Cross St Pancras. They 'roll back' between Warren Street and Oxford Circus.

 

[si404]

It's so the level interchange at Euston can be paired northbound to northbound and southbound to southbound.

 

[AM9]

In some cases, it is a historic consequence of lines being extended, e.g. White Cit Central line where the previous formation of an anti-clockwise loop is now used as part of the main running lines. More recent layouts are designed to optimise interchange flows, reducing the amount of interconnecting pedestrian traffic through tunnels. In reality, whether left or right-hand running is practiced, in separate deep tube tunnels, that is irrelevant to ordinary passengers.

 

[TRAX]

Ah I see that makes sense ! I can’t see a similar situation for the Northern Line example, why is it also the case here ?

 

[Bletchleyite]

Ah I see that makes sense ! I can’t see a similar situation for the Northern Line example, why is it also the case here ?

Because the lines run roughly east to west, so north-south is in opposite directions when they meet, if you see what I mean.

 

[TRAX]

No I don’t get it, sorry.

 

[transmanche]

Ah I see that makes sense ! I can’t see a similar situation for the Northern Line example, why is it also the case here ?

That's probably a bit more complicated. The station at Borough was constructed by the C&SLR so that the northbound tracks/platform are above the southbound tracks/platform (this often occurred to keep a railway underneath a road and avoid having to pay for expensive wayleaves for tunnelling under a property). The arrangement of tracks towards the King William St was 'somewhat complicated' and further complicated by the diversion of the route to London Bridge and beyond.

If you look at the Wikipedia article for the C&SLR there's an excellent engineering diagram of the original route, which is probably the best explanation.

 

[PeterC]

Because the lines run roughly east to west, so north-south is in opposite directions when they meet, if you see what I mean.

So by changing at Euston and Kings Cross in turn you can spend the whole day going "north" and end up where you started.

 

[TRAX]

I see but couldn’t this have been done nonetheless while keeping the classic track position ?

 

[transmanche]

I see but couldn’t this have been done nonetheless while keeping the classic track position ?

At Euston? No. Look at the map. Look at platforms 3 & 4, the northbound platforms. If you moved them to be north of platforms 5 & 6 (the southbound platforms) how are you going to 'thread' the tunnels through? And do it without closing the Northern line for a few years. All for the sake of looking 'neat'?

 

[TRAX]

No I’m talking about the Northern situation between Elephant & Castle and Moorgate.

 

[bramling]

No I’m talking about the Northern situation between Elephant & Castle and Moorgate.

I think the generally accepted explanation is that the *original* line to King William Street was built this way, primarily because it was decided to built the most difficult tunnel first, which was that closest to London Bridge (as in the bridge) and closest to the bed of the river - which meant the easternmost tunnel was the higher of the two. With the need for the tunnels to converge for passing beneath a narrow street north of the river, and with King William Street station being somewhat higher, it was therefore natural that the easternmost / higher tunnel became the northbound in order to give it the easier gradient up to the terminus. When the line was extended to Moorgate, this had to be continued as there was insufficient space to roll the tunnels over until north of Bank.

Possibly the more interesting question is why the C&SLR chose to revert to left-hand running south of Borough, when they could have just built the whole railway with right-hand running. I've never really seen an answer to that.

 

[transmanche]

No I’m talking about the Northern situation between Elephant & Castle and Moorgate.

I posted a response to that in post #8.

 

[TRAX]

I get it. Thanks everyone for the answers !