Faller is a German company specializing in making scenery and plastic model kits for model railroads. Their product line contains houses, trees, bridges and terrain accessories in HO, N, TT and Z scales.
Of particular note is Faller's "Car System" in both HO scale and N scale, which consists of small motorized road vehicles that have a magnet attached to the front steering. The magnet follows a steel wire hidden under the road surface, resulting in trucks and buses that behave in a realistic fashion without the need for unsightly guide rails.
Mechanisms are also available to stop vehicles and to switch them from one route to another, as at an intersection. These can be integrated with sensors and working traffic lights to create a realistic operating scene.