TMC means Traffic Message Channel
TMC is a system that uses many navigation systems. TMC receives RDS radio signals that contain traffic information. This is information about road works, traffic jams, and any redirects. The navigation system can then decide to suggest another route, to avoid the traffic jams. The TMC reception is free and is broadcast in the Netherlands by several radio stations. The information comes From the Tellussen that are on the road and are supplemented with information from the Government (road works) and the Police (accidents).