Turnpike doubles are 45-48 foot trailers and a RM double is a 45-48 footer with a 26-28 pup.
On the west coast Oregon and Idaho run triples, 3 26-28 foot trailers. The LTL companies and UPS/ Fed Ex run them a lot. There are other states that allow them and some states only allow them on certain highways.
I'm pretty sure double 53s aren't allowed in the US. I've only seen them in Canada.