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Last Updated: Monday, 25 February 2008, 14:47 GMT
How do car-share cameras count humans?
The Magazine answers...

A motorway
Car share lanes have not taken off in the UK
A new road camera that counts car occupants by detecting blood and water content on skin is being tested. How does it work?

Enforcing the more-than-one-occupant rule of car-sharing lanes has been a problem ever since Leeds opened the first in 1998 on the A647.

Using council officers and police is labour-intensive and ordinary CCTV can be fooled by dogs or inflatable humans.

But a solution could be provided by a new camera that counts humans by detecting the unique "signature" provided by the blood-water content of human skin.

It detects human skin
Then it counts heads
It's at least 90% reliable, says its creator, and not fooled by animals, dummies or cosmetics
Its infra-red beam penetrates the windscreen and takes two images of the inside of the vehicle, enumerating the number of people. It is being tested in Leeds.

Experts at Loughborough University believe this system, called the "dtect" camera, is the most effective.

Loughborough's Dr John Tyrer - director of the firm Vehicle Occupancy and who has been working on this project for six years - says the experience in Leeds suggests that without enforcement, offending is very high.

Graphic of how car-sharing camera could work
1: When triggered by approaching car, camera illuminates the windscreen area with two different wavelengths of infrared light
2: Two digital infra-red pictures of the windscreen are taken and instantly processed
3: System detects human skin from its blood and water content
4: Then it counts faces, eliminating hands and dummies

Using police officers is very costly and accuracy is only 55-60%, due to visibility issues partly from tinted windows or differing skin tones, he says. And CCTV cameras can mistake a dog for an individual or miss a small person entirely.

"We wanted to be able to spot humans, as opposed to inflatable dolls and mannequins. We thought 'What is humanness?'

"We couldn't go on skin pigment, but infra-red rays see all skin in the same colour."

Blood and water is one of the things that determines we are human, he says, so he developed a system that detects human skin.

When a vehicle comes into view the camera installed at the side of the road is triggered by a built-in vehicle detection system.

Green splodge

The camera instantly illuminates the windscreen area with two different wavelengths of infrared light. Two specialised digital infrared pictures are taken of the windscreen.

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The system is programmed to detect the blood and water levels in skin and then it uses certain algorithms to distinguish faces, as opposed to hands.

Within a fraction of a second, the vehicle occupancy count is determined using on-board electronics. If the car has more than one occupant, then it does nothing.

"But if it can only find one person in the car, it says 'whoops' and records the number plates and other information saying 'Here is the driver.'"

However at this stage the driver retains a right to privacy, so his face is "splodged" in green. But the time, date and speed are recorded.

Car-sharing camera
The cameras are being tested in Leeds
That information can then be stored on a local network or transmitted via wireless, to an automated traffic management system or to a terminal elsewhere for human processing.

There are "extraordinary circumstances" that prevent it being 100% accurate, says Dr Tyrer, but he believes his technology has the potential to eventually enable variable road charging based on occupancy numbers. And it could spark a significant increase in the number of car-share lanes.


But Paul Watters of the AA says there are doubts about its reliability.

"If approved by the Home Office it needs to be 100% reliable. People could be at the receiving end of a hefty penalty so to be falsely prosecuted would be abhorrent.

"At the moment this is new technology being used on moving traffic. Vehicles are different types and sizes, with different windows and different heat systems.

"This is very radical. Other countries use manual enforcement."

Other motoring organisations have raised doubts about the principle of the lanes, saying there is not enough road space.


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