How wide are the tunnels at Praed Street Junction?

[Hutch]

Victorian lithographs are known to take great liberties with reality. On page 1 of “Steam to Silver” (LU Museum, 1970) there is an example showing a broad gauge (?) train taking the H+C line westbound with three tracks coming towards the viewer who is “stood” in the mouth of the Gloucester Road –bound tunnel. The artist makes it look very wide – much wider than I suspect it is.

Can three lines be squeezed into the tunnel between PSJ and Edgware road ? – it would make for some interesting layout changes.

BTW, I strongly suspect the artist has misunderstood the six rails that would have been present in the dual gauge track layout at that time.

[Deleted]

The lithograph is full of literary licence, IMHO. First of all, it is usually dated as 1863 - AFAIK, Praed Street Junction did not exist in 1863, as the Praed Street station wasn't even built until well after the Met had opened.

Second, there were never any broad-gauge rails on the western side of the Circle Line - the junction was built well after broad-gauge workings had begun to fall out of favour; this made the construction of the tunnel much cheaper, as they could build it to the standard loading gauge instead of the broad loading gauge.

Third, the H&C route is actually the diverging route - I think the original tunnel curve was built under a curved road or an intersection, which is probably why the junction is where it is.

[Deleted]

hutch said:

Can three lines be squeezed into the tunnel between PSJ and Edgware road ? – it would make for some interesting layout changes.

Sadly not. If they could then it would mean eastbound H&C trains could go into Edgware Road wthout getting in the way of the District trains waiting to get in to Edgware Road.

[Deleted]

Which moves onto the next question, is it possible to widen the tunnel to create the room for three tracks? As you say the improvement for services into Edgware Road will be substantial if the three tracks did exist.

[Deleted]

The existing tunnel between Edgware Road and Praed Street Junction is already larger than it should be, due to the generous loading gauge provided for broad-gauge trains. Unfortunately, given the location of the tunnel and the inherent difficulty of expanding a cut-and-cover earthwork, widening it sufficiently and appropriately to provide three tracks would be so horrendously expensive that it would only be done as a last resort - i.e. the tunnel was about to collapse.

Once you actually had a three-track tunnel though, then you could build something like this, for example.

216.55.161.203/theonekea/underground/diagrams/edgware-road-layout.txt

While on the surface the merits of such a layout appear strong, citysig has already said that the way Edgware Road is worked (i.e. timetabling), it would not be as useful to have a side-separated junction of this sort. Therefore, there really isn't any point in widening the section between Edgware Road and Praed Street unless it becomes absolutely necessary.

[Phil]

hutch said:

Victorian lithographs are known to take great liberties with reality. On page 1 of “Steam to Silver” (LU Museum, 1970) there is an example showing a broad gauge (?) train taking the H+C line westbound with three tracks coming towards the viewer who is “stood” in the mouth of the Gloucester Road –bound tunnel.

I don't know which edition of S to S you have, but my edition clearly shows TWO broad gauge (dual gauge) tracks with a pretty accurate 6-ft between them! Sure you're not being confused by a 'trompe d'oeil'?

[Deleted]

There's plenty of room - all that's needed is to re-gauge the entire sub-surface sytem to metre gauge ;D

[stanmorek]

The structure over Praed Street junction is G105 and comparing the Victorian artists impression (see link below) and inspection photos it is a true to life representation! It's appearance hasn't changed at all apart from possible addtional plate lining between girders.

Plans of the G105 show it to be 117' long and have 15 arched girders with the widest spanning 55' and the narrowest 32'.

www.hurstmereclose.freeserve.co.uk/html/london_transport_steam.html

[Hutch]

rbruce1314 said:

I don't know which edition of S to S you have, but my edition clearly shows TWO broad gauge (dual gauge) tracks with a pretty accurate 6-ft between them! Sure you're not being confused by a 'trompe d'oeil'?

Guilty as Charged !! I can see now looking at the coloured picture pointed to by Stanmore K that it is indeed twin dual guage track. T1KEA's comments are noted that this branch may never have actually had broad-guage tracks.