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Experimental feature

As more cars clog the world’s roads, governments are looking for an answer to the increasingly fraught problem of congestion.

One approach is to charge vehicles by tracking them using the Global Positioning System (GPS) satellite network. Operated by the US Department of Defense, GPS allows a user to detect their position on the earth’s surface to an accuracy of about five to 10 metres. A GPS unit in a car can record where drivers go and charge accordingly.

The UK Department for Transport’s proposed scheme to track all cars by satellite has boosted the profile of this technology but many smaller projects are already up and running around the world.

Switzerland charges lorries to use its roads on a per-kilometre basis, with a system that records distance travelled from the truck’s odometer and cross-references it with GPS readings. In Germany, a toll system for trucks based on satellites has been in place since early this year.

Road charging schemes are under consideration around the world, including Japan, South Korea, India and China, says John Dowson at IBM business consulting services.

“It’s not just a European phenomenon,” he says.

However, many road charging schemes rely on less space-age technology. Austria’s motorway toll scheme uses short range microwave technology to track lorries passing toll points. The city centre congestion charge in London uses cameras and number plate recognition software.

But GPS offers the possibility of extending the system to cover a network of roads, varying charges by time of day, and even pricing roads dynamically in response to traffic flows.

However, GPS is significantly more expensive and still relatively new. Germany’s experience illustrates the potential troubles of the system well. Originally scheduled for 2003, it did not start until 2005 although a two-year delay is not too bad given a novel and ambitious project covering 448,500 vehicles on 12,000 km of motorway.

Nonetheless, some users still have complaints. Karlheinz Schmidt, general secretary of BGL, the German hauliers’ association, points to several areas of concern for his members.

It is, he fears, too easy to evade. “You can go for days without being controlled,” he says. One driver’s on-board computer failed without him noticing. “He didn’t get caught for four weeks,” says Prof Schmidt.

Harald Lindlar of Toll Collect, the consortium which operates the system, says that less than three per cent of tolls are being evaded.

Prof Schmidt also claims that drivers have been receiving bills with some surprising information. For example, one driver was told he had crossed the same motorway crossroads four times in rapid succession in the same direction - clearly an impossible journey.

This illustrates one of the problems with GPS technology. The precision of the system varies according to conditions, and can’t be relied on 100 per cent of the time. Buildings, forests and so forth can block the path between satellite and receiver, compromising accuracy. Even if it could be, say, 99.9 per cent accurate, the 0.1 per inaccuracy will still generate a considerable flow of complaints from 500,000 users.

To overcome the inherent flaws in GPS, it has to be combined with other systems. “On its own I don’t think that GPS will ever be enough. There are technologies which complement it, which enable you to validate what is happening,” says Mr Dowson of IBM.

Germany’s system relies on about 300 gantries which detect when lorries enter the motorway network and work out whether they have a satellite box on board. Boxless lorries are photographed and pursued for fines. The boxes contain a dead reckoning system, based on gyroscopes similar to those used in aircraft, which can tell where a truck is going if it loses touch with the positioning satellites.

This combination of technologies makes it harder to fool the system, but it also drives up cost, and makes it harder to get the project up and running, as Toll Collect found out.

“The project was much more a systems integration project, rather than a mobility project,” says Mr Lindlar. This was why, after the project’s initial teething troubles, Deutsche Telekom’s systems integration subsidiary, T-Systems, became the lead partner in the consortium.

GPS is already more expensive than alternative systems. The German system required an €500 unit to be installed on each truck, not to mention the multi-billion euro cost of other infrastructure required.

Many cars already have navigation systems on board and it might be possible to install the charging system on those as a software application. But it is not something manufacturers are prepared for yet.

“It’s not on our roadmap,” says Stephan van Kruisselberge, global head of marketing at satellite navigation device manufacturer TomTom. “At the moment we are not looking at it, mainly for privacy reasons.”

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