Road magnets help cars to navigate

March 12, 2014 // By Christoph Hammerschmidt
Automated driving requires very exact positioning methods - in many cases the accuracy of a GPS system is not good enough. Volvo engineers had an interesting idea: Magnets, embedded in the road, could help the vehicles to determine their exact position.

Positioning techniques typically used in automated driving schemes such as cameras or GPS (or, perhaps, in a couple of years, the more exact Galileo) hit their technological limits under certain conditions. Volvo engineers had the idea to engulf ferrite magnets in the road - unlike the abovementioned techniques they remain unaffected by physical obstacles and poor weather conditions; the system was designed to provide a positioning exactness of better than 1 centimetre.

A trial conducted with the road magnets at a variety of speeds now has been concluded, and according to Volvo the results are encouraging. It acknowledged the accuracy predicted - and it appears that the technique even offers additional features. Besides supporting the exact navigation required for automated driving, it also could support driver assistant system that prevent run-off road accidents. The magnets could also facilitate the accuracy of winter road maintenance. As a more indirect effect road space utilisation could become more effective - the accurate positioning gained through the magnets could allow authorities to build narrower lanes.

For the test, Volvo equipped a short road stretch of 100 metres with a pattern of round ferrite magnets with a size of 40 x 15 mm. The magnets were placed 20 cm below the surface. The test vehicles were equipped with several magnetic field sensors. The test was designed to evaluate relevant parameters such as detection range, reliability, durability and impact on road maintenance. According to Jonas Ekmark, Preventive Safety Leader at Volvo, the trial proved that ferrite magnets are an efficient, reliably and relatively cost-effective solution with regards to both the road infrastructure and the sensing equipment in the cars. The next step will be conducting such a trial in real-life traffic, the expert announced.