I don't know about the track or race aspects. Convex mirrors are pretty common on road cars, especially on the passenger's side. Split mirrors seem to be common on vans. And the warning message has a Wikipedia page of it's own! Jonathan PS: I've seen parodies of that message, was it on BlatChat... ? PPS: They're very unlikely to be lenses, and Newton would be greatly offended. :-) PPPS: Isn't it about time that external mirrors were replaced by video technology?