What's best for the environment, a well thumbed map and some common sense, or a satnav? To find out, Tiawanese researchers Wen-Chen Lee and Bar-Wen Cheng from the National Yunlin University of Science and Technology recruited 32 drivers and asked them to navigate to a series of pre-determined locations; half of them were asked to get there by satnav, the other half had to use a map. The team monitored the progress of the drivers and clocked the distances they travelled. In all cases the Satnav triumphed. On urban routes journeys were on average 7% shorter than when the driver followed a map, and even in the open country routes remained 2% shorter. Since shorter trips on average use less fuel, they are more enviromentally friendly. But satnav may also improve driving safety, Lee points out, because the map users consistently changed course more times per journey than their satnav-guided colleagues. More course changes can be a sign of frustration, which can lead to dangerous driving.