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Katy O'Sullivan, traffic light controller at TfL
Photograph: Andy Parsons

Things you only know if you control London’s traffic lights

James FitzGerald

…according to Katy O’Sullivan, 27.

Traffic lights were invented in London 150 years ago

‘The first signal was installed in December 1868 in Parliament Square. Obviously, it’s now imprinted in your brain what red, amber and green mean – but originally, there was a lot of confusion. Also, the lights were gas-powered and, after a month, they exploded. The idea was only brought back in the 1920s.’

London’s traffic light HQ is like something from a movie

‘At Transport for London’s control centre in Southwark, we’re in charge of timings for all the city’s 6,000 traffic lights. We have access to around 5,000 CCTV cameras across London, and we watch the road network 24/7. We also have detectors in the ground to monitor how much traffic there is at each junction and even what type of vehicles they are. People ask me if it’s like living in “The Matrix” – and you do have a lot of power. If you make a change to the lights to help one place, you have to deal with an impact elsewhere on the network.’

Traffic lights aren’t supposed to slow down traffic

‘Our goal isn’t to stop traffic, it’s to keep it moving. For example, we once noticed that cars exiting a couple of supermarkets weren’t getting enough green time at the lights because of extra Christmas demand, so we increased the timings just for the holidays. I really like that a small thing can make a big difference to people’s journeys.’

Many people can’t believe it’s a job at all

‘If there’s an area we can’t see on camera, we go and do a physical check. People find it strange to see me there, staring at a traffic light for up to seven hours a day. They often ask me if I’m lost or offer me a cup of tea or a chair to sit on. And they’ll usually tell me about another set of traffic lights that they want me to go and have a look at.’

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