Satnav gives directions for a greener route

location based services

Following the fastest route offered by an in-car satellite navigation system has become second nature to many motorists. When it comes to minimising greenhouse gas emissions, however, the best route might not be the fastest nor even the shortest.
Now Eva Ericsson at the Lund Institute of Technology in Sweden has been testing a satnav system that has been programmed to work out the most efficient route. In tests on the streets of Lund, Ericsson and her colleagues Hanna Larson and Karin Brundell-Freij have shown that their satnav system can work out routes that are significantly less polluting than the standard options.
The team assigned fuel consumption factors for three types of car on 22 streets in a satnav's digital map database. These were based on the street's class - which took account of information such as its width and speed limit - and typical traffic flows in both peak and off-peak hours.
Ericsson and her colleagues report that the average fuel saving on the 22 streets was 8.2 per cent compared with journeys planned by other methods (Transportation Research C, DOI: 10.1016/j.trc.2006.10001). None of the streets was particularly congested, however, and Ericsson estimates that savings on most journeys would be closer to 4 per cent.
A probe car was also driven around the same 22 streets sending real-time traffic flow data by radio to the satnav system. The researchers hoped that this would improve the choice of route still further, by showing where there were traffic jams, but it turned out that one probe car is not enough. At least 50 per cent of jams need to be detected to make probe cars effective, but the lone car detected only 26 per cent of them.
Commercialising such a system will be no easy task, says Liévin Quoidbach at Navteq, a supplier of digital satnav maps based in Zaventem, Belgium. "Making the measurements to give every street in the world a fuel consumption factor will be too expensive," he says.
This does not necessarily rule out the Swedish team's idea. If enough drivers can be recruited to volunteer their cars as probe vehicles, such detailed map information would be unnecessary, they suggest.
James Tate at the Institute for Transport Studies at the University of Leeds, UK, says probe cars could also transmit data on their fuel consumption as they travel around. The fuel savings offered by such a system could be a good marketing tool for the makers.
From issue 2585 of New Scientist magazine, 04 January 2007, page 24