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Volvo Car Group tests road-embedded magnets for accurate positioning of self-driving cars

Volvo Car Group has completed a research project using magnets in the roadway to help the car determine its position. A pattern of round ferrite magnets (40x15 mm) was located 200 mm below the road surface. The test car was equipped with several magnetic field sensors. Click to enlarge.

Volvo Car Group has completed a research project using magnets embedded in the roadway to help the car determine its position. The research, which has been financed in strategic co-operation with the Swedish Transport Administration (Trafikverket), is a potential means of implementing self-driving vehicles.

Reliable and highly accurate positioning is one of the crucial issues in the development of self-driving cars. While established positioning technologies such as GPS and cameras have limitations in certain conditions, road-integrated magnets remain unaffected by physical obstacles and poor weather conditions. Accordingly, the use of road magnets has attracted some academic research, as well as a number of patents filed on different approaches.

As one example, the California PATH (Partners for Advanced Transportation TecHnology) Program at the University of California at Berkeley in the 1990s developed one such system using magnetic markers embedded under the roadway for lateral guidance. This system was demonstrated during the August 1997 National Automated Highway System Consortium Feasibility Demonstration, San Diego, CA, without a single failure.

The magnets create an invisible ‘railway’ that literally paves the way for a positioning inaccuracy of less than one decimeter. We have tested the technology at a variety of speeds and the results so far are promising.

—Jonas Ekmark, Preventive Safety Leader at Volvo Car Group

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. 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.

—Jonas Ekmark

In parallel with the potential in the field of autonomous driving, 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 utilization of road space since accurate positioning could allow lanes to be narrower.

Volvo Cars’ research team created a 100-meter 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 program was designed to evaluate crucial issues, such as detection range, reliability, durability, cost and the impact on road maintenance.

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.

—Jonas Ekmark

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.

—Claes Tingvall, Traffic Safety Director at the Swedish Transport Administration


  • Bento, L.C.; Nunes, U.; Moita, F.; Surrecio, A. (2005) “Sensor fusion for precise autonomous vehicle navigation in outdoor semi-structured environments,” Intelligent Transportation Systems, 2005. Proceedings doi: 10.1109/ITSC.2005.1520055

  • Han-Shue Tan; Guldner, J.; Patwardhan, Satyajit; Chieh Chen et al. (1999) “Development of an automated steering vehicle based on roadway magnets—a case study of mechatronic system design” Mechatronics, IEEE/ASME Transactions on doi: 10.1109/3516.789684



My post to the Toyota FCEV thread disappeared - twice!
I'm just posting here to see if the same thing happens.


No problems in this thread then.


This may become part of the solution, as complementary guidance to increase safety and security of autonomous drive vehicles.

Using 2 or 3 guidance systems could make autonomous drive vehicles much safer than a single bad driver?

Over 75% of all equipped road accidents could be avoided.

Reduction in fatalities and damages could be important leading to large reduction in insurance fees.


I don't know about this working. We can't even fill all our potholes, so maintenance will be a problem. I still favor some type of Persone Rapid Transit, which would replace the roads, and not require heavy personal vehicles around town.


Sorry, I stated that poorly. PRT will not replace the roads, but reduce the traffic on city streets.


Why not just use road lines - they are already there.

Road lines and GPS should give you what you need - long range and short range location.

No need for the embedded magnets.


The picture that comes with this article is misleading. In reallity the embedded magnets would be much farther apart, like 100 meters or so. And would only be used to update established positioning technologies such as GPS.


Volvo is a Swedish/Chinese company. Both countries have snow cover on the roads part of the year. Besides road lines get worn, especially in countries where studded tires are used during winter


Machine installed nail or screw type magnets would not be very costly and could last much longer than painted lines?

The idea is to have a complementary guidance system to increase autonomous driving safety and acceptance.

Bob Wallace

Google has apparently had some trouble with snow covered roads where the side lines can't be detected.

I can see coded positioning of magnets. Put two close together at the beginning of a straight section.

Position them closer on curves, letting the car track more carefully.


Are they talking about a TOY CAR?
What if someone throws a few magnets 2-3 feet away from the outside line of a sharp curve?
The car will simply keep going straight into a ditch, or down a ravine.


The magnets wouldn't be the only source of information, but would be one input in the positioning system.
Hopefully the system would be robust enough to detect malicious scattering of other magnets and so on.


Thanks, it makes sense now.
You have to have a multi-modal, robust system, with at least GPS/Glonass, road lines and magnets, and a simple INS (such as you have in phones nowadays).

The system will have to be able to work when 2 or 3 are missing. I.e. in a tunnel with the markings unclear and no magnets.

You could simply use radar or machine vision to detect the car in front and follow it (for short periods of time).

The beauty of the human brain is that it is naturally fault tolerant.
Building this into a navigation/driving system is non trivial.

On the other hand, a fly can navigate with a very tiny brain.

Maybe we need a new paradigm of automated driving.

I'm pretty sure this technology has been tested for decades now, retrofitting our roads with magnets is not a very economical way of bringing about the autonomous car. If the human eye can keep a car following a road, why can't a machine? Then again there is the snow problem, even humans have difficulty with that sometimes. In theory with very accurate GPS and a little AI a car should be able to follow a road blind, but we would need cellphone towers retrofitted to augment the GPS to achieve cm accuracy. What I'm getting at is if an autonomous car could follow a road BETTER then a human then schemes like retrofiting roads with magnets or hyper-accurate GPS might be worthwhile.


The trick would be to build systems which can optionally use magnets.

Thus, you could place them at accident black spots rather than the whole network, or the whole network in snowy places.

Humans can drive with simple binocular vision, but it is extremely difficult to program the "common sense" parts of this, not to mention the object recognition and scene understanding.

Bob Wallace

Tunnels may be the easiest things to navigate.

They are fixed. Their shape and length won't change. Just store that in the database.

The tunnel walls will give excellent positioning feedback.

I'm seeing the magnets as interesting solutions for places where snow accumulates on roads and some sort of magnetic guide for detours. Something that could be temporarily installed and moved as the project needed.

Store "start detour here - refer to magnets" information in the GPS/download system.

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