Chapter 3. Height of California Vehicle Code >> Division 15. >> Chapter 3.

No vehicle or load shall exceed a height of 14 feet measured from the surface upon which the vehicle stands, except that a double-deck bus may not exceed a height of 14 feet, 3 inches. Any vehicle or load which exceeds a height of 13 feet, 6 inches, shall only be operated on those highways where deemed to be safe by the owner of the vehicle or the entity operating the bus.

(a) A boom or mast which is designed to be raised and lowered by hydraulic mechanisms and which is a constituent part of or an attachment to a vehicle or machine, shall be securely chained or otherwise restrained to ensure compliance with Section 35250 while the vehicle or machine is being transported as a load or driven upon any highway.
  (b) Subdivision (a) does not apply when the configuration and design of the hydraulic boom effectively restrain the movement of the boom during transit.

(a) A pilot car may operate a vertical clearance measuring device with a height in excess of 14 feet when escorting a permitted overheight load. The pilot car may also operate the vertical clearance measuring device when surveying a route for a permitted overheight load.
  (b) Any vertical measuring device used by a pilot car shall be designed and operated so as to avoid any damages to overhead structures. The measuring device shall be securely affixed to the pilot car, and shall be operated in a manner that does not create a hazard to surrounding traffic.
  (c) The operator of the pilot car shall not reduce the vehicle's speed more than 20 miles per hour below the posted speed limit on the roadway to measure overhead clearance, nor exit the vehicle to measure the clearance of overhead structures from a vantage point on or above the roadway.