Different standards.
Out west, they have what's known as "Ports of Entry" where most any truck over 6,000 lbs (I think) has to stop. However if you go into one of these and say you are transporting PERSONAL household goods you'll generally be passed on. Even if you are driving a BIG truck. Motorhomes (so far) even with trailers, are pretty much exempt from stopping for weighing.
When I travel over the "weigh in motion" scales out on the highway, I'll often be electronically directed into the scales... I'm in a motorhome, though, and just drive on by and have never been stopped regardless of having a Gross Combined Vehicle Weight of sometimes approaching 80,000 lbs.
As always YMMV...
