Look out! The speed bumps that turn out to be an optical illusion

WHEN is a speed bump not a speed bump? When it’s an optical illusion painted on to the road in an effort to slow down drivers.

Transport for London (TFL) has enjoyed success after installing virtual speed bumps at 45 locations around the capital.

A design that presents an illusory bump to oncoming vehicles is being used in efforts to bring traffic speeds down to 20mph, amid concerns that drivers often ignore this limit.

TFL first used the idea on the A117 in the borough of Newham and bumps have also been painted on Southwark Street in south London. The virtual obstructions cost less and cause less disruption for motorists than installing the real thing – and speeds have fallen by 3mph at the trial sites.

Nigel Hardy from TFL said: ‘As part of these trials a number of different measures – including new signs, road markings and painted speed bumps – are being introduced to reduce traffic speeds. We will continue to try new speed-reducing ideas to save lives and prevent injury on our roads.’

Although TFL controls just five per cent of London’s roads, they carry 30 per cent of all traffic.

A number of boroughs across London have also adopted the idea. If the trials prove successful in London, local authorities across the country may be tempted.

However, councils around England have come under pressure from Environment Secretary Michael Gove to rip up speed bumps as part of plans to reduce pollution.

This is because motorists slow down and then accelerate between speed bumps, which increases emissions. Virtual speed bumps, assuming they work, will do exactly the same – which may prevent them from being adopted more widely.

The painted speed bumps are just one of a number of imaginative ideas used by planners to try to make roads safer.

Cambridgeshire County Council used inlaid bricks to create a ‘fake’ roundabout last November, although it cost £500,000 and critics said it could encourage drivers to mount the pavement.

India has one of the worst road accident rates in the world but it has found success with 3D zebra crossings that appear to rise out of the road. A similar design was also used successfully in China.

And in 2010, a school in Vancouver, Canada, used a 3D optical illusion of a young girl chasing a balloon across the road to try to make drivers slow down near its gates.