Rare mixed tube track Baker Street

Rare mixed tube track Baker Street

The UK’s railways have one type or another of rail which are flatbottom or the increasingly rarer bullhead. London’s underground still has a fair bit of bullhead although this is gradually being replaced with more modern flat bottom rail. Although sections of flatbottom and bullhead can often be found connected end on with special spacers and fishplates to keep the different types of rail correctly aligned. If the engineers decide to weld them together it means no special fittings are required.

Very rare arrangement of flat bottom (nearest) and bullhead rail (furthest) on the same section of track!

The same applies on the tube, you can find sections of track with either one or the other but not two different types of rail mixed on the same section of track. It can be done but its rare practice anywhere on the UK’s railways and if undertaken correctly its not a problem. One has been able to find examples of short sections of either type of rail overlapping on the main line railways so it can be done.

However longer sections of such mixed use are even rarer. One can find substantial sections of flat bottom with bullhead check rail and there are special rail chairs made for this mixed type use but its not common. On my journey home this evening I was surprised to find an exceedingly rare use of both flat bottom and bullhead on the same stretch of Bakerloo Line track.

This unusual arrangement will probably last just a day or two.

1972 tube stock arriving at Baker Street with the mixed rail section clearly visible.

Over the past year or so TfL have been undertaking track improvement works at several stations on the Bakerloo (such Warwick Avenue, Edgware Road and Baker Street – not always at the stations themselves but in the tunnel approaches.)

The standard method of laying down full length sleepers complete with chairs into the concrete base of the tube tunnels is a time honoured one. The sleeper is set and its ends embedded in fresh concrete. When this is set solid the engineers then cut the middle section of the sleeper away. This is the method being used at Baker Street. Its used on the other tube lines too, not just the Bakerloo.

At Warwick Avenue and Edgware Road a different method is used because its a more modern arrangement of setting the track.

The old bullhead rails on the northbound Bakerloo prior to track renewal.

Its very rare to lay a new flat bottom rail on one side and reinstate the bullhead on the other because it invariably means extra work has to be done in taking out the rail keys, the bullhead itself and then the old rail chair – that is before even installing a new rail chair chair and then fitting the flat bottom rail itself to the new chair.

The idea of using complete sleepers every fourth position during track replacement work on the deep level tube helps to lay the rails down faster and also sets their distance apart correctly.

If one has to switch the chairs and then install a different rail instead at a later possession its not exactly a time saver.

The spacing of the temporary sleepers can be easily seen in this view.

In some situations however it can save time because it means only the one rail has to be replaced – even though it still means the correct rail chairs and flat bottom rail has to be installed at a later time.

There are a quite few reasons why this method would be used. Its probably essential when overnight possessions are considerably short, or have to be stopped suddenly or earlier than anticipated – or it might just be difficult delivering both sets of rail to the site itself and so it has to be split into more possessions. Or the lengths of track further along are unequal because of previous repaired track. Alternatively it could be the presence of particular track circuits that this method is required – and it must be stressed there is a junction immediately beyond the northbound platform!

Clearly it was planned at some stage of the works and it was probably decided to do the job in two lots.

It just means less time is required during a subsequent night possession in order to replace the other rail. Normally the work is done in one possession – depending on the length needing to be replaced – this rarer method simply requires the use of two shorter possessions even though the actual work itself takes a little longer.

Being so used to the tube its a fair frequency when one sees rail replacement undertaken it happens on all the lines and fresh sets of rail are a frequent sight. However one usually sees a complete pair of brand new rails in place the next morning rather than this unusual combination of new and old rail.

Its just extremely rare to see a partial job done. It must be absolutely stressed this rare method used at Baker Street is not a problem. It is an absolutely safe method and the trains’ operation or safety is not compromised in any way at all.