California Code, Vehicle Code - VEH § 35401.1

A combination of vehicles operated pursuant to Section 35400 or 35401 with a kingpin to rearmost axle measurement of greater than 38 feet but not more than 40 feet may be operated on those highways under the jurisdiction of local authorities only where it is deemed to be safe by the owner of the vehicle or the person operating the vehicle and where its operation is not specifically prohibited by local ordinance pursuant to subdivision (d) of Section 35401.