I think alot of these odd configurations we see going down the road are doing it illegally, and havent been sighted yet, and yes heavy trucks have to conform to these laws also. Max. length on a single trlr. is 53ft. and doubles are limited to 28ft per trlr. max. There is this thing called the federal bridge law that deals with the length issues and it is so complicated and lacking in any sence I wont even begin to explain it, even if I could, correctly.