the system consists of a forward-facing camera, which scans the road ahead for traffic signs. This camera is connected to character recognition software, which then makes a note of any changes described by the signs, and relaying it onto the car’s instrument panel.
The information stays there until any change occurs, so if a driver is unsure of the current speed limit all they have to do is check the information that the car has noted.
The technology is being developed by many automotive suppliers, including Continental and Delphi. It uses Image processing techniques to detect the traffic signs. The detection methods can be generally divided into color based, shape based and learning based methods.
Vienna Convention on Road Signs and Signals is a treaty signed in 1968 which has been able to standardize traffic signs across different countries. About 52 countries have signed this treaty, which includes 31 countries from Europe. The convention has broadly classified the road signs into seven categories designated with letters A to H. This standardization has been the main drive for helping OEMs develop a traffic-sign recognition system that can be used globally.
The first TSR systems which recognized speed limits were developed in cooperation by Mobileyeand Continental AG. They first appeared at the end of 2008, on the redesigned BMW 7 Series, and the following year on the Mercedes-Benz S-Class. At that time, these systems only detected the round speed limit signs found all across Europe (e.g.).
Second-generation systems can also detect overtaking restrictions. It was introduced in 2008 in the Opel Insignia, later followed by the Opel Astra and the Saab 9-5. This technology is also available on the 2011 Volkswagen Phaeton and, since 2012, in the Volvo S80, V70, XC70, XC60, S60, V60 and V40, as a technology called Road Sign Information. They are not able to recognize city limit signs, which in most European countries are associated with speed limits, as they are too similar to direction signs.