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Spy in the cab

The Highways Agency's 1M, state of the art road inspection vehicle is set to revolutionise highway maintenance, says Richard Thompson.

Visiting the Transport Research Laboratory is like stepping into a James Bond film at the point where Bond visits Q - the boffin behind all his gadgets. And the latest gadget being developed at the Crowthorne research centre could certainly fit into any Bond scenario.

For the past four years the TRL has been employed by the Highways Agency to develop the Highways Agency Road Research Information System (HARRIS). HARRIS is a van, crammed full of state of the art technology, that can carry out and analyse full road surface surveys while driving at traffic speed. The rear of the vehicle, developed at the TRL, carries a complex system of computer controlled cameras that can spot tiny cracks in road surfaces while travelling at up to 80km/h. At the same time lasers on the front, supplied by Danish specialist manufacturer Greenwood Engineering, carry out a detailed road profile survey.

Early detection of cracks in road surfaces is crucial for prolonging the life of roads. A typical road substructure can last for up to 40 years providing the surface does not deteriorate and allow water to permeate through. However, a typical asphalt road surface is only expected to last about 10 years, depending on the traffic. The cost of maintaining a road can, therefore, be massively reduced by early detection of cracks.

'There are three reasons for developing HARRIS,' explains Highways Agency project manager Les Hawker, 'Currently inspection surveys are performed manually. This requires lane closures while engineers carry out a visual inspection. HARRIS reduces such disruption to traffic. It also allows more consistent data collection by removing the subjective judgments of site personnel. Most importantly, it provides a safer system of work by removing people from the road.'

Spotting cracks relies on 24, 70W fog lamps mounted underneath the HARRIS vehicle, behind the rear axle. These create an intense 50mm wide strip of light across the road lane. 'The light beam is contained inside a skirted enclosure,' explains TRL senior researcher John Pynn. 'This prevents outside shadows interfering with the beam.'

Three line cameras mounted inside the vehicle above the light strip each scan a 1m long by 2mm portion of the road. An electronic shaft encoder linked to the rear axle triggers the cameras every 2mm of travel.

'This means the image is unaffected by the speed of travel,' says Pynn. 'Therefore each one shows exactly the same thing.' After 1m of travel the 2mm strips are compiled to form a single video frame. This is recorded onto a standard VHS video recorder. Location information is automatically added.

However, the video does not make recommended viewing. 'The vehicle is capable of covering up to 300km a day,' says Pynn. 'Watching the footage might make a good cure for insomnia but for inspecting a road surface it would be easy to miss defects.'

Fortunately, HARRIS can carry out the analysis as well. An on board computer instantly converts the analogue video image to a reduced digital image. A standard personal computer can then run special crack detection software to analyse all the digital images and produce a list of all the cracks in the road surface.

According to the Highways Agency, HARRIS can be used on all types of road surface. Initially the vehicle has been developed for priority issues, particularly cracking, but in time it is hoped to extend to other defects such as 'fatting up', where bitumen rises to the road surface.

One thing not shown in the Bond films is the amount of work that has gone into developing Q's gadgets. Similarly, the Highways Agency has spent around 1M over the past four years developing HARRIS. Pynn himself has spent nearly 25 years researching systems for automated crack detection. 'It has sometimes been a case of waiting for the technology to catch up with the ideas,' he sighs.

Also on board the HARRIS vehicle is a sophisticated road profiling system provided by Danish specialist manufacturer Greenwood Engineering. There are 25, 16KHz laser sensors mounted on the front of the vehicle to measure the shape of a 3.6m wide strip of road every 100mm travelled by bouncing beams off the road surface. An on board processing system combines this profile data with longitudinal profile data recorded at the same time to produce a three dimensional image of the road.

The HARRIS vehicle is currently experimenting with a Trimble global positioning system that will link the HARRIS data to Ordnance Survey co- ordinates. 'This will allow us to monitor specific locations over a number of years,' says Hawker.

The Highways Agency is hoping that a private manufacturer will take up HARRIS with a view to marketing it worldwide. Hawker is very excited by its potential. 'We think HARRIS will increase road inspection productivity by 15 to 20 times,' he claims.

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