Noisy Barbican tube trains #2

Noisy Barbican tube trains #2

Historical knowledge of rail vibrations

London Underground has known for decades there is a problem with tube trains making noises. There have been complaints since the first trains ran underground in 1863. However that is probably something that was largely accepted in those days (just as there was soot, steam, heavy machinery continuously at work in factories, horses’ hooves making loud cacophony in the street and so on.)

Matters apparently changed in 1955 when London Underground were asked to investigate effects of noise and vibrations from the tube encroaching into a hospital. London Underground conducted experiments in February 1955 to see how far away these vibrations could be felt. The affected premises was the now closed Leytonstone House Hospital (around 400 feet (120m) from the Central Line a short distance from Leytonstone station.) The hospital had found the tube line quite intrusive. Remember the Central Line had just opened this section thus it was a new phenomenon the hospital was experiencing.

The advantage of conducting these special tests at this location was it afforded information on both the overground tube track as well as tunnelled tube track (this being the newly opened extension to Newbury Park/Hainault.) Using a Vibrograph from Cambridge measurements were taken in differing rooms, with different floor coverings on both the ground and first floors of the main hospital buildings. The tests found the vibrations could be felt this far away from the Central Line and in fact the direction of the trains could be discerned too. Not only that the noise from the trains could easily be discerned too on the hospital’s ground floor but less so on the first floor.

Sixty five years later it was acknowledged by TfL this section of the Central Line was in fact the noisiest section of tube to be found anywhere on the network. It was found the noise was much worse when the trains were packed with commuters. Last year TfL began a programme of track renewal and improvement to abate this problematic section of the Underground.

TfL say they have no information on what are the loudest sections of London’s tube system. I wonder how they found out this section at Leytonstone was the noisiest? Further they say they do not record data on tube noise, nor are resources on the tube specifically aimed at the reduction of tube noise!

The use of different types of track

Generally it seems traditional bullhead jointed rail has caused less problems than continuous welded rail or the more modern track fastenings such as Pandrol clips etc. Pandrol clips are practically the industry standard but even so these have had to be developed to help try and mitigate noise problems on railways. The latest types are the e-clips, the fast clip, and others where the interface between the clip and the rail itself is insulated by way of a special tough plastic mount to prevent noise and vibration transfers occuring.

However it seems even the more recent methods do not completely resolve the issues, especially if its welded rail. The traditional bullhead rail used wooden blocks and these were no doubt a factor in deadening the sounds from the rails and the wheels of the trains. Conversely concrete sleepers as opposed to wooden sleepers are a problem as every urban railway operator will know. Concrete sleepers are practically maintenance free but unfortunately make the noise and vibrations far worse.

In the past couple of years TfL has used concrete sleepers far less and increased the use of wooden sleepers for the moment at specific locations on the tube system because of the ever increasing problem with rail noise. However they say its not ideal because its becoming harder to source wood that is sustainable.

Quite why continuous rail would be more noisy than jointed I cant say for sure, but its probably something to do with the harmonics of vibrations and how these travel through materials. One would have thought the noise would be dissipated more, but obviously not. There’s lots of research and equations to show why this happens. In a nutshell its simple physics. Continuous welded rail is fraught with varying forms of resonance which carries the noise further depending on various conditions such as temperature, composition of the steel, malleability and so on.

With jointed track the actual path of the vibrations would be quite limited because it is cut short by the joints between the rails. Plus the wooden keys used to fasten the rails deaden the sounds too. With continuous welded track the vibrations simply continue regardless.

In short it seems the more advanced railways become, the more critical the infrastructure too becomes in terms of noise frequency and so on. And any change in set up (introduction of new rolling stock etc) upsets the balance greatly.

In 1998 London Underground acknowledged replacement of a stretch of track had caused part of the Circle/District Lines at Notting Hill to become even more noisy. They had said ‘the track in that area had recently been replaced with ‘continuous welded rail’ as part of a routine maintenance programme which should have reduced noise levels.’ However it had got worse. ‘In January 1999 LUL admitted that they did not understand the causes of the problem and commissioned experts to review the case and prepare a plan of action to resolve it. They subsequently stated that they understood the problem to be one of ‘poor dynamics of train wheels and rails’ in the area.’

Clearly its a question of ever changing dynamics. Replacing jointed bullhead rail with continuous welded invokes a different harmonics in terms of vibration and noise and so on. Thus the floating slab track in the Barbican has evidently invoked a new set of harmonics which has altered even more perceptibly now the new S7/S8 stock has been introduced. In short what worked to an extent in those early days doesn’t work these days!

The tunnels today

This image is the best I know of showing the bridge-like structure of the tube lines underneath the Barbican. Yes the tube trains do run above these vast empty concrete chambers in the depths of the Barbican! Source: Guerrilla Exploring. (The page seems to have been deleted thus an image from the Internet Archive is used here.)

The tracks are suspended above and the whole structure sits on these beams which are in turn placed upon thick sheets of rubber mats (or rubber bearings to be exact) to absorb any vibrations. Secondly there is also a gap between the tunnel wall and the structural basement walls of the Barbican itself as can be seen on the right hand side.

There’s something of great interest in this picture. It seems to me the rubber bearings are deteriorating. And its why someone has placed bricks in the gap – no doubt to keep the structure level and prevent it dropping down in to the gap should those crumbling rubber bearings fail completely. If this did drop the tube trains would suddenly be faced with a short, sharp dip in the track – not doing the riding quality much good – and passengers would also be greatly annoyed!

A close up shot of one of the rubber bearings. As can be seen its rather primitive!

This picture shows the air gap between the tunnels and the foundations of the Barbican. Where possible this air gap was built so as to reduce noise from the trains. Unfortunately its only on part of the entire length of new tunnel built through the Barbican. Here again one can see bricks have been used to prop up the railway tunnels!

If one knows the Barbican estate well enough in some parts one can actually be standing next to the tube line tunnels themselves! Its not a forbidden thing to do because these are public access areas. Its just the Barbican is a quite a maze and unless one is a frequent visitor or lives nearby one will generally use just the main, busier, public areas. I used to live nearby during the eighties and nineties so know it well.

I took this picture inside one of the car park areas in the Barbican. The train tunnels themselves run behind the wall on the left. Note there is a gap in the ceiling. If one were to get a ladder and climb up into that space they would be able to see the top of the Metropolitan, Circle and Hammersmith tunnels!

The tunnels’ location can also be seen in other parts of the Barbican where service roads run. That leading to the basement of Brandon Mews has a hump where it crosses the tunnels.

What the residents want

What do the Barbican residents want? Obviously the cessation of the constant noise and vibration that has been plaguing the estate for nigh on fifty years. The discomfort to residents is generated from around 5 am to just before 1 am. Complaints have been ongoing since the 1970s without any real resolution being found. As my research shows, its not that any sudden change in the set up has caused complaints to begin. Its just that the first residents had not moved in the affected parts until the seventies, and no doubt they noticed the problems straightaway.

TfL has relaid some track with new welded sections. It also found sections of track where rail joints needed maintenance. In August last year TfL did an experiment in the later part of an evening where trains were made to run much slower, 15mph rather than the usual 35mph. This showed the noise generated by the trains was enormously reduced.

Unfortunately TfL’s plans are to increase the number of trains through the Barbican, perhaps by 2023 or thereabouts. The present works to automate the tube are part of this and the aim of this is to be able to introduce a much more frequent service than can currently be operated with manual train driving. Evidently some are not going to be pleased at any attempts by TfL to increase the frequencies on the Metropolitan, Circle and Hammersmith lines!

TfL say they are introducing a new type of rail fastening clip which its hoped will go some way towards resolving some of the issues of noise . Source: What Do They Know

One of the earlier programmes to improve track in the Barbican area (2016) though this is not the most recent or the exact noise affected areas. The newer type of Pandrol rail fastenings can be seen. Source: Twitter (Note: This picture is from one of the TfL social media accounts deleted in September 2020 thus an archived image is used here.)

The Barbican residents now want TfL to make the experimental speed restriction conducted last year permanent. As one will no doubt guess that is at odds with TfL’s plans to increase service frequency. What’s more is the residents want part of the track system underneath the Barbican closed down for good:

What we would like to see is the removal of the crossovers, where the trains can switch between the eastbound and westbound tracks to Aldgate that’s really key and we would like TfL to have a higher maintenance budget. The Barbican is a particular instance, when it was built the tunnel the trains run on between Barbican and Moorgate station is actually an integral part of the structure of estate so people living in some of the blocks are living in concrete-framed structures that are directly linked to the concrete box through which the trains run and it’s a brilliant way of transmitting noise and vibration to people’s homes. Source: City Matters

Clearly one of the demands from the Barbican’s residents is the crossovers below Brandon Mews have to be removed. TfL has said this is not possible. However it has too said in other documents if the current crossover at Liverpool Street could be relocated (its within the platform area at the moment which is not ideal) and upgraded, it might be possible to dispense with the Moorgate ones. If that happens it of course would mean no more trains to Moorgate.

The derelict Thameslink platforms and track on the old Moorgate lines – this could form a solution to the various problems in the area…. if only!

The closure of the Moorgate terminus platforms would also mean TfL have a massive asset on their hands – a huge white elephant – and one they could not do much about. That’s because at the time of writing a brand new development is being built above the station site and the plans are fixed. There’s no way the structure could be altered now to accommodate the space left vacant by the four Moorgate terminus platforms.

A possible solution for the Moorgate trains?

There’s a possible solution to it all but it seems TfL is not offering this in any sense or any form. What’s that then?

Its the fact the old Widened Lines tunnel from Farringdon to Moorgate (closed in 2009) could be reused for these short workings that currently terminate at Moorgate. As some of us have said, these tunnels could be used to turn Metropolitan Line trains at Moorgate and thus release capacity on the lines through the Aldgate triangles. Oh no! TfL don’t want the tunnels for that! They want the tunnels for stabling of their trains. Peace and quiet for their non sentient trains but not so for the Barbican residents!

Crossrail has nearly finished its works at Barbican which means the tunnels will be available for the use of trains to Moorgate. The is the view of the tunnels as they head under Smithfield.

The fact these tunnels are not in use at the moment means they are vacant and can be re-used to adopt the very latest floating track designs which are proven to be resilent and would be of great benefit to the Barbican. It would mean trains could terminate at Moorgate without having to go through any crossovers – these crossovers could actually be sited underneath Aldersgate Street (just to the east of the Barbican platforms) instead and each track thus becomes a reversible route into Moorgate. Its no difference in terms of scope and distance from the new crossovers west of King’s Cross station when they need to use this as a terminus and trains are not running eastwards from here due to engineering works or the route not being available due to an incident etc.

In fact TfL have built new junctions at Farringdon but its not for trains in passenger service. Rather its for the series of new stabling sidings they hope to establish along the former Farringdon to Moorgate Widened Lines corridor.

The defunct Thameslink platforms at Moorgate.

Why cant TfL just put this new junction and proposed stabling lines lines into passenger service and re-arrange the layouts so that there are absolutely no points underneath the Barbican? It would mean the need for crossovers in the old, problematic parts of the tunnel would no longer be needed and the tracks could be plain lined and welded throughout the problematic areas to reduce further noise from the through trains. No more tube trains banging and clattering through a series of points!

I am aware this solution has been mooted oft times before – and TfL are not wanting it. Just thought I’d mention it anyway!

Just for the memory! I took this pic of a Connex South Central 319 at Moorgate loaned to Thameslink, due to form a Luton service. May 2003.

Clearly TfL are forging ahead with their automation plans and in due course the section from Euston Square to Aldgate will be converted to CBTC control. And no, it seems they cant do it all over again just to build new tracks and junctions between Farringdon and Moorgate and refurbish the platforms at both stations for passenger services. Thus some apparent lovely new ideas that offers huge potential for noise reduction in the area are sadly a no-no.

What I think it means is the Barbican residents won’t be seeing any sort of solution they would like in the near future. Instead of just those very annoying crossovers on the lines into the four Moorgate platforms, there will also be extra crossovers in order to implement TfL’s plans to use the old tunnels as stabling sidings! Just can’t win!

Some of the images (and the track slab plan I modified and used) were from this City of London document.