:Good point! I don't have a ready reference, but I remember reading something about this distantly ... if someone else can find a reference. There are two problems: 1) A half-track also has the disadvantages of both wheels and tracks, the tires are not as rugged as tracks, the tracks are not as quiet as tires, and not suitable for high speeds or delicate uses, 2) The system is inherently more mechanically complicated. Any basic auto mechanic will have an idea how to fix a flat tire, but ... a broken track? Cheers,