Lights, camera... gridlock: The technology behind CCTV

London's traffic is controlled by 20 people in a single office. Simon Usborne discovers the hi-tech art of going with the flow

'Ooh, you don't want to be getting a flat tyre there," says John Tenten, watching one of the six flatscreen monitors on his desk. "Not good, not good at all." With a practised flick of his right hand, Tenten pans the CCTV camera right, using a joystick, before twisting it to zoom in on the hapless motorist. A man is crouched on the pavement, struggling to change the wheel of a maroon people-carrier.

Tenten is sitting on a black leather chair that Blofeld would approve of, deep in the bowels of an unremarkable old building in Victoria in London. The windowless room hums with the sound of more than 60 monitors and a TV wall showing a map of the capital. Staring in silence at their screens, 20 men and women have one of the toughest jobs in Britain: they run the London Traffic Control Centre (LTCC), which keeps the city ticking and its increasingly clogged arteries flowing.

It's rush hour on Thursday afternoon. Watching the small drama of jack and wrench unfold from the serenity of this room, it's clear that Tenten is right: the infamous six-lane gyratory system at Hyde Park Corner – scourge of learner drivers and cyclists alike – is one of the worst places in the city to break down. And if there's one thing Tenten, a manager at LTCC, hates, it's breakdowns. And roadworks. And people parked on red routes, crashes, errant lorry-drivers and all the other things that conspire to congest the streets.

Traditionally, the cure for these ills is to install more traffic lights, road markings and signs. But people are now asking whether this makes things worse in a city that only gets slower. Next week, the Commission for Architecture and the Built Environment (Cabe), the Government's urban planning advisers, will publish a paper, Civilised Streets, which poses the question: is there another way?

The document will look at "shared space", a radical approach to urban design that is sweeping parts of Europe. In a handful of Dutch and Scandinavian towns, traffic lights have been ripped out and kerbs flattened to show that cars and pedestrians can co-exist without signals – and without killing each other. In one Swedish town, a shared space initiative led to a significant reduction in accidents and congestion as drivers took more care and slowed down. A similar project will be trialled this year in Exhibition Road in west London, home to the Natural History and Science museums.

Could this be the beginning of the end of the traffic light? Tony Earl, another LTCC manager, is sceptical: "London is not a small town in Sweden. Without traffic lights, the network would collapse and the city would grind to a halt. Simple as that." But, even with the lights, driving in London at rush hour these days is horrendous. The much-quoted average speed is 9mph; a horse could do that without breaking sweat.

Earl says public perception of gridlock in the capital is a big challenge for the LTCC. "Traffic has become a huge political issue," he says. "Ten years ago, people accepted traffic jams, which weren't as bad anyway." What's made them so bad since? Bendy buses? "They carry more people, so their overall impact is to reduce traffic. They're just another vehicle we have to get through London." Cyclists? "There are thousands more of them on the roads, but we can deal with those." Just too many cars? "Well, we're certainly at capacity. We haven't got room for any more roads; that's it."

Sometimes, you can't help thinking that capacity has already been exceeded. If everything's running perfectly, the streets flow, but the smallest incident can trigger a crisis. Flat-tyre man, who's come to a halt on Grosvenor Place beside the Queen's garden at Buckingham Palace, is still floundering. In minutes, the traffic backs up. If he doesn't get a move on, he could single-handedly bring gridlock to Hyde Park Corner and its six major tributaries.

"I saw Elephant & Castle lock up once," says Earl, shaking his head as he talks about another of the capital's congestion hotspots. "Nasty business. It spreads out like a virus. When you're working at capacity, the tiniest event like this can cause chaos."

Our digital eyes on Hyde Park Corner are one of 1,200 CCTV cameras the LTCC uses to help prevent jams by spotting the first signs of trouble. We switch our attention to the feed from a camera at Cambridge Circus, where Shaftesbury Avenue crosses Charing Cross Road. I spot a van parking illegally. Tenten tuts, and passes me the controls. I move the joystick to dip the camera for a better look. Nothing happens, so I push again, and the camera drops violently, skipping straight past the van. "Other people will be watching this feed. They'll know you're an amateur," Tenten says, resuming control.

Keeping London moving is about more than watching it. The latest simulation software allows traffic control engineers at the LTCC to build three-dimensional maps of existing or proposed junctions, adding vehicles programmed to behave like the real thing, whether they're bendy buses or boy racers. The data the software spits out helps to improve the phasing of lights and traffic flow, and to assess the impact of an event such as a demonstration, or of road works.

These simulations are used to create sequencing patterns designed to cope with different problems. So, if a tailback is growing at Angel in Islington, the operators can click on the plan called "Congestion building on Upper Street". In future, the LTCC hopes that such simulations will allow managers to predict the outcome of a serious jam or crash in minutes and to plan a rapid response.

Increasingly, nobody has to click on anything to keep traffic moving. The Split Cycle and Offset Optimisation Technique, fortunately, has a snappier acronym: Scoot. It can automatically measure traffic flow and respond instantly, controlling the single most important weapon in the LTCC's impressive arsenal: traffic lights.

Greens, ambers and reds have spread across the country since the world's first traffic light, a gas-powered affair, blew up outside Parliament in 1869, injuring the policeman operating it. London alone has more than 6,000 sets of lights. Half are left alone to change at fixed intervals. About 1,000 run according to timing plans (main roads get more green time at rush hour, for example), which are reviewed every couple of years. Hardly cutting-edge. But the remaining 2,000 sets of lights, which control the capital's most crucial junctions, are smarter.

Buried in the tar a few yards short of these lights, electro-magnetic sensors scan the road four times a second, determining the speed and volume of traffic approaching, or waiting at, the lights. They feed the information to four LTCC computers that are programmed to adjust the phasing of those lights and others near by to maximise the flow of traffic.

So, when Tower Bridge lifts, Scoot sensors immediately notice a slowing of traffic. To stop massive queues forming on the approach roads, Scoot tells the surrounding lights to green-light vehicles crossing the approaches or moving away from the bridge. As a result, vehicles waiting to cross the Thames are slowed and held at junctions surrounding the bridge, not just on the approaches. When the bridge is lowered, Scoot clocks the now moving traffic and reverses its work. The technology also works to recognise and give priority to buses at many other junctions. And no one has to lift a finger.

But, sometimes, humans have to intervene. The biggest challenge in Tenten's 34-year career (he started out sending traffic reports from his motorbike by radio, long before CCTV and Scoot) came at morning rush-hour on 7 July 2005. He was in charge at the LTCC. "As soon as we started hearing reports of incidents, and saw the number of emergency vehicles, I knew this was something very serious," says Tenten, who also worked during the IRA bombing campaign.

An hour after the Tube bombs that day, the LTCC switchboard received hundreds of reports of an explosion on a bus. Callers suggested different locations for the explosion. Using their cameras, Tenten and his staff on the morning shift quickly saw, on the big screen, exactly what had happened to the No 30 at Tavistock Square. "For some of the guys, it was very upsetting," Tenten recalls. "It was quite graphic."

The LTCC confirmed the location of the bomb blast to the police, and a still picture from its camera showing what remained of the bus became one of the enduring images of that day. It would be another 30 hours before an exhausted Tenten left the floor and headed home.

Tenten plans to retire in a couple of years, but he'll be back for the LTCC's next big challenge – the 2012 Olympic Games. As part of the capital's Olympic bid, LTCC chiefs were asked to convince the Olympic delegation that they could keep athletes and officials moving. They screened a real-time video of a car being "green waved" along the "Olympic highway", from Hyde Park Corner to the stadium site in Stratford, east London. Helped through the capital by Scoot, the LTCC car made the 10-mile trip in 21 minutes, half the typical average time.

The traffic on Hyde Park Corner is moving nowhere near that fast as, 20 minutes after he came to a stop in Grosvenor Place, flat-tyre man is still changing his wheel. But then he packs away the jack and drives back towards Victoria. "He's off," says Tenten, as another rush-hour draws to a close. "Good job, too; that could have been a bad one."

Driving us crazy: how the capital's streets stack up

*Laid out end to end, all the roads in London would stretch for 8,500 miles – about the distance from the city to Australia.

*A relatively small 400 miles, or 4 per cent of the total, comes under the direct control of the LTCC, run by Transport for London. But these routes include names synonymous with gridlock – the Hanger Lane gyratory, Trafalgar Square, the A40 – and carry almost 40 per cent of the traffic moving around the capital.

*Every day, 21 million motor vehicle journeys are made in London, from moped pizza deliveries to supermarket deliveries and school runs.

*Almost 7,000 buses carry about six million passengers a day on more than 700 routes.

*Half a million cyclists travel on London's streets every day.

*Each year, there are 500 road closures caused by public events, from the Notting Hill Carnival to the Tour de France.