The American demonstration project PATH shows the possibility of automatic driving using information from infrastructure. The vehicles are equipped with sensors, which detect magnets placed on the road.
The installation of a test field with simple permanent magnets, which are placed within the road and which alternate between North and South poles for every 1,2-Meters, produces a binary code when driving over the magnets. From the codes of 25 magnets information about the road characteristic (Curves, Gradients) results. The American model uses as far as possible inexpensive, ceramic permanent magnets, and for the areas, where magnetic steel is close to the road surface, stronger neodymium magnets are used. For lane guidance the PATH project demonstrates that it is likewise possible to analyse the magnets with three sensors for an exact determination of position. However small distances (1.2 m) between the individual magnets are necessary. According to the information collected the vehicles are automatically driven. Through vehicle to vehicle communication, each vehicle in the lane is informed about the reactions of the surrounding vehicles.
The model project from America shows the feasibility of autonomous lane guidance in accordance to equipped infrastructure and vehicles. For the mixed operation on regular motorways however, additional installation of systems are necessary, which cover conventionally driven vehicles and evaluate mechanisms for obstacle recognition. The prerequisites for this form of automatic driving in mixed traffic consisting of conventional vehicles and vehicles equipped with autonomous driving systems could probably not be created in the next few years, and hence separate lanes would have to be created for magnet sensor systems for the time being.