Here is the wording from the CA DMV
"Towing Vehicles, Buses, or Large Trucks
When you tow a vehicle or trailer, or drive a bus or three or more axle truck, you must drive in the right hand lane or in a lane specially marked for slower vehicles. If no lanes are marked and there are four lanes or more in your direction, you may only drive in either of the two lanes closest to the right edge of the road."
A three axle motor home is not considered a truck or bus, so if it is not towing it is not required to follow the regulations for a bus or truck, just like it is not required to stop at weigh stations. As long as they are less than 45', they are considered 'house cars'. However anything over 40' does require an upgraded driver's license.
The towing signs in CA are being updated to specify any vehicle towing anything is restricted to 55 mph.
I am in NM now, but have just spent the last three days travelling through AR, MS, OK, TX and NM. Most of these states have interstate speed limits of 70 or 75 mph, with no towing restrictions. So if you want to get out in the fast lane and run with the big boys (semi trucks) have at it. Personally I keep to my 62-63 mph while towing just like I do on the open roads of CA, where I spend most of my time. ;)
