10 engineering wonders of London’s transport history

When the world’s first underground railway opened in London in 1863, the only trains available were steam powered. Engineers had to work out how to operate steam trains safely underground and reduce the steam and smoke. 

Engineers used conventional steam locomotives, but the solution was to fit special pipes to condense the exhaust steam into side tanks of cold water. This meant less steam in the tunnels, but smoke was still a problem. Coke was used instead of coal as it creates less smoke, and there were ‘blow holes’ at intervals around the railway, but the atmosphere underground was still very unpleasant. The pollution problem was eventually overcome by electrification in the 1900s. 

The first tunnels for the underground railway were built just below ground using the ‘cut and cover’ method. This involved digging a huge trench, laying track, building a brick archway and then resurfacing over the top. Building tunnels deep underground through London clay presented a different set of problems. The tunnels had to be strong, and wide enough for trains to travel through. 

The invention of the Greathead shield, named after its creator James Henry Greathead, revolutionised tunnelling. It allowed circular tunnels to be built deep underground lined with strong iron rings. Tube tunnels were built up one ring at a time behind a shield. As the shield moved forward through the clay, the curved sections were quickly put in place – all by hand – before the tunnel walls could collapse. Today it is done by machine, though the principle is the same. 

Operating a railway deep underground means you need to find an efficient way of getting passengers down to the platforms and back up to the surface. 

The solution was hydraulic lifts, powered by pressurised water. They were installed at stations on London’s first tube railway, the City & South London Railway, which opened in 1890. There are two cars in the shaft, each capable of carrying 50 people. The lifts were reliable, but slow. Much better than having to climb up and down over 100 steps though! 

With the introduction of deep-level tube railways from 1890, steam locomotives could no longer be used because of the lack of ventilation. 

Electric traction was used to power the trains instead and electric locomotives were designed to fit in the smaller tube tunnels. The electricity used by the locomotives was generated by a small power station in Stockwell, and later at Lots Road in Chelsea, which was the biggest power station in Europe when it opened in 1905. 

Early railway signals and points were operated by large levers in signal boxes, connected by rods and wires to the equipment out on the ground. It was physically demanding work for the signalmen and the levers took up a lot of space. 

The new Tube railways built in the 1900s introduced colour light signalling and compressed air-operated points that could be controlled from compact power lever frames. This technical advance meant less space was needed for equipment and a lot less physical effort from the signalmen. The frame has an illuminated diagram showing the position of a train passing through the section of track. The wooden cabinet houses a complex mechanism that prevents points and signals being set in dangerous combinations. 

At the beginning of the 20th century, the Underground was at the cutting edge of technology, always looking for new ways to get ahead of the competition.  

An experimental, spiral moving walkway was installed in a spare lift shaft at Holloway Road station in 1906. It was patented by William Henry Aston and built by Jesse Reno, the American inventor who went on to develop the first working escalator. The spiral elevator was not a success and never operated in public service, but the first escalator was successfully installed at Earl’s Court in 1911. 

Electricity is generated by power stations in the form of high voltage alternating current (AC), but Underground trains operate using a Direct Current (DC) system. 

Mercury arc rectifiers converted the high voltage current from AC to DC at 600 volts. The rectifier is mounted on insulated struts and would have had safety barriers all around it because the exterior steel tank filled with mercury was ‘live’ with electricity when in use.

After the First World War, passenger numbers on the buses increased and a vehicle with more capacity than the predominant B type of the time was required. But the police controlled the licensing regulations and these placed limits on vehicle size and weight. 

Engineers at the London General Omnibus Company designed the K type, introduced in 1919, which seated 46 instead of 34 passengers. The driver’s seat was moved next to the engine instead of behind it and the body was made wider but with arches over the wheels. Consequently 12 more people could be accommodated in a design that was similar in size and weight to the vehicle it replaced. 

Trams ran on fixed rails in the road. Maintaining the tracks cost a lot of money and passengers had to step out in the middle of the road to board the vehicles, which wasn’t safe. 

In the 1930s, London Transport began to replace trams with the trolleybus, which was a cross between a tram and a bus. It had an electric motor like a tram, powered through overhead wires, but it ran on rubber tyres like a bus, not on fixed rails. With no track to maintain, operating costs were lower. Passengers found trolleybuses easier and safer to use because the vehicle could pull into the kerb. 

London Transport’s experience making aluminium-bodied bomber aircraft during Second World War stimulated development of a new type of bus that was easier to operate and maintain and used fuel more efficiently. It was also needed to replace the trolleybus network in the late 1950s, which due to overhead wires required more maintenance. 

Engineers designed the Routemaster, a bus that had a lightweight aluminium frame, which reduced the strain on the engine. The Routemaster also had interchangeable body parts, making maintenance quicker and more efficient. Bus drivers welcomed the new power-steering, which made the vehicle much easier to drive.