California Code, Vehicle Code - VEH § 35785

(a) The axle weight limitations imposed in Sections 35550 and 35551 shall not apply to the transportation of a single saw log which does not exceed 8 feet in diameter and 21 feet in length or 6 feet in diameter and 33 feet in length, if such log is hauled on a combination of vehicles consisting of a three-axle truck and a two-axle logging dolly under permit issued by the Department of Transportation or by local authorities with respect to highways under their respective jurisdictions. Such permit may be granted for not more than thirty (30) days and may be revocable upon notice by the department or local authorities, as the case may be.

(b) When so transported, the vehicle shall not be operated over any bridge or causeway at a speed of more than 15 miles per hour or on the highway at more than 25 miles per hour, on routes designated in the permit. Diameter measurements of the logs shall be made on the large end.