Volvo Car Group has completed a research project using magnets in the roadway to help a self-driving car determine its position.

Reliable and highly accurate positioning is one of the crucial issues in the development of self-driving cars.

Established positioning technologies, such as GPS and cameras, have limitations in certain conditions but road-integrated magnets remain unaffected by physical obstacles and poor weather conditions.

Jonas Ekmark, preventive safety leader at Volvo Car Group, said: "The magnets create an invisible ‘railway' that literally paves the way for a positioning inaccuracy of less than one decimetre. We have tested the technology at a variety of speeds and the results so far are promising."

Volvo Cars plays a leading role in a large-scale autonomous driving pilot project in which 100 self-driving Volvo cars will use public roads in everyday driving conditions around the Swedish city of Gothenburg.

"Our aim is for the car to be able to handle the driving all by itself," said Ekmark."Accurate, reliable positioning is a necessary prerequisite for a self-driving car.

"It is fully possible to implement autonomous vehicles without changes to the present infrastructure. However, this technology adds interesting possibilities, such as complementing road markings with magnets."

Road-integrated magnets open up a number of other possibilities:

• Incorporating magnet-based positioning in preventive safety systems could help prevent run-off road accidents.
• Magnets could facilitate accuracy of winter road maintenance, which in turn could prevent damage to snow-covered objects, such as barriers and signs, near the road edge.
• There is also a possibility of more efficient utilisation of road space since accurate positioning could allow lanes to be narrower.

The research was financed in strategic co-operation with the Swedish Transport Administration (Trafikverket).

Volvo Cars' research team created a 100-metre long test track at the company's testing facilities in Hällered outside Gothenburg, Sweden.

A pattern of round ferrite magnets (40x15 mm) was located 200 mm below the road surface. The car was equipped with several magnetic field sensors.

The research programme was designed to evaluate crucial issues, such as detection range, reliability, durability, cost and the impact on road maintenance.

 Ekmark said: "Our experience so far is that ferrite magnets are an efficient, reliable and relatively cheap solution, both when it comes to the infrastructure and on-board sensor technology. The next step is to conduct tests in real-life traffic."

Claes Tingvall, traffic safety director at the Swedish Transport Administration, said: "The test results are very interesting, especially when adding the potential for improved safety as well the advantages for the development of self-driving vehicles.

"A large-scale implementation of road magnets could very well be part of Sweden's aim to pioneer technology that contributes to sustainable mobility."