http://www.dot.ca.gov/hq/traffops/signtech/bus-motorhome/
Key statements:
45' Motorhome: On this web page, a 45' motorhome refers to a single-unit motorhome that is longer than 40 feet but not more than 45 feet.
The basic California length law for vehicles is 40 feet unless specifically exempted. On October 9, 2001, Governor Davis signed Assembly Bill (AB) 67 which changed the California Vehicle Code (CVC) to allow motorhomes over 40 feet in length, up to 45 feet, on certain routes.
The CVC requires a motorhome endorsement on a noncommercial class B driver license issued by the California Department of Motor Vehicles (DMV). The pertinent CVC sections are copied below under "Legal History."
The driver must pass a written and skills examination (i.e. a driving test), submit a specified medical form, and pay a $34 fee. The medical exam must be repeated every two years. The license is valid for approximately five years.
Out-of-State Drivers: Non-residents visiting California may not operate a motorhome over 40 feet in length unless in possession of an out-of-state driver license authorizing the operation of that vehicle.
LEGAL ROUTES
Access Routes: 45' motorhomes may travel on virtually every State route EXCEPT those signed with a 30-foot kingpin-to-rear-axle (KPRA) advisory sign. This sign advises trucks with a KPRA of more than 30 feet not to use the route. There are also KPRA advisories signs with 32, 34, 36, and 38 feet. These advisories that are 32 feet and higher ALLOW 45' motorhomes to use the routes.
On-Line Map: See: http://www.dot.ca.gov/hq/traffops/trucks/bus-mh/45-bus-map.htm. Click on the red numbers to open each regional map.
Restricted Route List: An on-line list of route segments that restrict 45' motorhomes is at: http://www.dot.ca.gov/hq/traffops/trucks/bus-mh/45-bus-restrict.htm. The list includes beginning and ending post miles and intersecting streets or highways of each segment.
Stopping for Services: 45' motorhomes may exit the designated route for fuel, food, and lodging provided the access is safe, and provided the service is within one road mile of an "identified" exit. The exit must be identified to show that the service route has been evaluated and approved by State and local engineers. Currently, the only identification system for service exits is a "Service Access" sign, which is an "S" on the back of a truck, as illustrated below. These signs were intended for large trucks, and are located primarily on the interstates.
City and County Access Roads: Caltrans has jurisdiction over State routes only. 45' motorhomes are allowed on certain State routes, but not necessarily on local roads. Cities and counties have jurisdiction over local roads. To inquire about motorhome access on local roads, contact the appropriate city or county public works department.