Retrotechtacular: London Bus Overhaul

If you have ever visited London as a tourist, what memories did you take away as iconic of the British capital city? The sound of Big Ben sounding the hour in the Elizabeth Tower of the Palace of Westminster perhaps, the Yeoman Warders at the Tower of London, or maybe the guardsmen at Buckingham Palace. Or how about the red double-decker buses? They’re something that, while not unique to the city, have certainly become part of its public image in a way that perhaps the public transport of other capitals hasn’t.

A city the size of London has many thousands of buses in the fleet required to provide transport to its sprawling suburbs. Until a few years ago the majority of these machines were built to a series of standard designs under the London Transport banner, so a Londoner with an eye for buses could have seen near-identical vehicles in any corner of the city. Each of these buses would have carried millions of passengers over hundreds of thousands of miles in a typical year, so many in fact that every few years they would have required a complete overhaul. For that task, London Transport maintained a dedicated factory capable of overhauling hundreds of buses simultaneously, and this factory is our subject today.

The overhaul works at Aldenham was the subject of a 1957 British Transport Films picture, Overhaul, in which we follow a bus in its journey through the system from tired-out to brand-new. We see the bus given a thorough inspection before being stripped of its upholstery and then having its body separated from its chassis and cleaned, then we see each part being refurbished. Along the way we gain a fascinating insight into the construction of a mid-century passenger transport vehicle, with its wooden frame and aluminium exterior panels being refurbished and rebuilt where necessary, before the camera. Meanwhile we see the chassis, with its separate gearbox in the centre of the vehicle, before it is painted to resist more years of road grime and reunited with a bus body. The completed vehicle is then taken for a test run before being sent to the paint shop for a coat of that iconic London Transport red. Enjoy the film in its entirety below the break.

The buses in the film are the AEC/London Transport “RT” vehicles, which entered service in the late 1930s and last ran in the 1970s. Their replacement, the visually similar “Routemaster” had only started to appear the previous year, and continued in regular service until 2005. Meanwhile the Aldenham bus overhaul works survived until its closure in 1986 due to the appearance of a range of new buses in the capital that did not conform to the standard design that it had been designed to serve.

48 thoughts on “Retrotechtacular: London Bus Overhaul

    1. “it would be interesting to see a train overhauled” – fittingly, the Aldenham works was originally built for an extension of London’s Northern line from its current terminus at Edgware to a new terminus at Bushey Heath, just past the Aldenham works. Work on the extension was stopped in 1939 due to the outbreak of World War 2, with the incomplete buildings retrofitted into a bomber factory. Following the war legislation designed to stop London absorbing surrounding towns meant the extension was cancelled, leaving London Transport with a massive partially complete facility which they then adapted to service buses.

      The unmentioned real killer for the Aldenham facility was Margaret Thatcher’s 1980s privatisation of the country’s bus services which led to the aforementioned balkanisation of the buses, making a centralised facility next to impossible.

    2. “…. it would be interesting to see a train overhauled.”

      That is one thing I can actually say I’ve been witness to: I worked at GE Transportation for about 2.5 years in their diesel engine plant in Grove City, PA. One of the fantastic things about that place was that it was non-union, which meant that if you wanted to get up to your elbows in engine grease, then the shift guys would be more than happy to have you. There’s nothing quite like gutting a 4400 hp engine and watching all the pieces get cleaned and put back together again.

  1. “If you have ever visited London as a tourist, what memories did you take away as iconic of the British capital city?”

    I got beaten by a pack of 4 “doctors and engineers” and had my phone stolen. Police was like ‘meh, it happens’.

  2. When I moved to London at the end 1969 to work for the BBC, there were still RT’s around, but mainly RM’s (Routemasters), which had the same overhaul cycle. Reputedly they would run between 500K & 1M miles between complete overhauls. The design was such that it was easy to swap out mechanical parts for servicing, so it was sometimes easier to change a badly performing engine than try to fix it in situ. Travelling on a recently overhauled bus was like being on a brand new one, which in effect it was.

    British Rail had a similar system, which continues to this day. The power cars for the HST/IC125’s are stripped, and refurbished from the ground up. The engine/alternator sets are sent back to Paxman to be rebuilt, as are the bogies and drive motors, which go back to the manufacturers. I remember seeing the drive motor line at Brush Engineering in Loughborough in the early 90s. Dozens of motors in various stages of assembly, and lots of heavy electrical gear for testing them.

    A different time.

  3. My mate works at the Transport Museum in London, he’s quite high up, gets to head projects. All sorts of interesting stuff to say about his job. He’s renovated early 20th-Century busses and old tube carriages and allsorts.

    Also somehow that makes him technically an employee of London Transport. So he gets free travel, worth a bleedin’ fortune itself in London.

    1. I wonder if he knows anything about the really old (WW1 era) double decker bus that was seen several times in Downton Abbey, Mr. Selfridge and (IIRC) early episodes of Call the Midwife?

      1. I know he’s done a horse-drawn one, and one who’s structure was based around a giant chunk of wood, basically the core of a tree. I think the latter was an early motor bus. He took it on a tour round the UK.

  4. During my recent trip to England (sorry I missed you, Jenny!), I was surprised to see the lorries haul cars stacked 3 up!
    Later I speculated that because underpasses on the M highways allow double decker busses to pass under, there is enough room for taller truck trailers than here in the States.

    P.s. if England is Metric, why are the speedometers and motorways in MPH, and bathroom scales reading out in stones?

      1. You mention the one thing that is unlikely to change too soon. The cost to the taxpayer for changing EVERY roadsign in the UK from miles to kilometres would be phenomenal. Almost all cars/bikes on UK roads have speedometers registering both mph and kph and this has been the case for a number of years.

    1. There is no height limit but for practical purposes you should be under 4.9m to fit under all motorway bridges. Anything over 3m in height must have the height labelled in the cab in fairly large type and visible to the driver.

      We weren’t always metric. Somethings are best left alone.

      Those car transporters are pretty cool themselves. A really well thought our engineered solution. I think the max is 16 cars on one of them but still coming under the 4.9m height and under the max length limit.
      Lots of hydraulics to play with :)

    2. That’s a European thing I think, mostly to do with the more restrictive legislation on truck sizes, so they pack them in very tight rather than just being able to make the truck bigger / longer. Same reason 99% of European trucks have the cab over the engine.

    3. We use both imperial and metric (although if I have to do any maths then I convert everything to metric). And while most of the road signs are in miles, at junctions you’ll sometimes see them in metres. Oh, and we buy our petrol by the litre but measure consumption in miles-per-gallon. Pretty much ever ruler or tape measure has inches on one side, and centimetres down the other, and if you buy a set of spanners you’ll usually get a set of metric and a set of imperial.

  5. For some reason I expected to see some welding.

    This is awesome to see. Once these things go fully electric, if they ever do, I take it overhauling the bottom-half would be a bit easier. No oil, little coolant, self-contained battery packs, smaller electric motors, etc.

    1. Bendy buses have all caught fire and taken out of service, havnt they?
      As a motorcyclist in London when they had them they were bloody dangerous.
      The roads just wernt wide enough and if youve been beside one on a bike when they start to turn you soon learn to give them a wide berth. The driver cant see anything down the side.

    2. Over here in Seattle, Sound Transit is phasing out the bendy busses in favor of double-deckers. They’re much shorter, and carry more people. I imagine they’re cheaper to maintain, too.
      No thrilling joint to ride inside of, sadly.

  6. “If you have ever visited London as a tourist, what memories did you take away as iconic of the British capital city?”

    Tower bridge is obviously popular, but I don’t think many people ever go to see the steam engines that are in the basement of it, its well worth a look if you get a ticket for the bridge. I think they used to power the bridge but its probaly all electric nowadays.

    Any suggestions for not-so-obvious places to see in London for engineering/science enthusiasts?

    1. Try the London Museum of Water and Steam. They have several large steam engines that they run at weekends, including a 90 inch water pumping engine they run once a month. Seeing such a huge piece of 19th century engineering in action up close is quite something.


    Unitrans in Davis, CA still operates the original RTs in regular scheduled service. I believe it is the only transit system in the world to do so since London retired theirs. I drove for Unitrans while in school at UCD and after 500 hours of driving regular modern buses, I was eligible for training on and operating the vintage double-deckers. They come complete with no power-steering nor power-brakes, and the transmissions are preselector type. Loads of fun!

    One of the RTs had the diesel engine swapped out with a new natural gas one.

  8. I used to work in the bus industry in Liverpool. We had a council run depot like this until the early 90’s and it carried out the same process as this on similar vehicles until the mid 80’s. A lot of people I worked with were there at the time and they all had some great stories to tell. Something else that also happened was that they employed a lot of ‘unemployable’ people too, people with disabilities and mental health issues, which is something the modern commercialized bus industry doesn’t make room for anymore. I dare say most major cities would have had a similar setup and they would have been very interesting places to work!

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.