Section 22406. Maximum Speed for Designated Vehicles
No person may drive any of the following vehicles on a highway
at a speed in excess of 55 miles per hour:
(a) A motortruck or truck tractor having three or more axles or any
motortruck or truck tractor drawing any other vehicle.
(b) A passenger vehicle or bus drawing any other vehicle.
(c) A schoolbus transporting any school pupil.
(d) A farm labor vehicle when transporting passengers.
(e) A vehicle transporting explosives.
(f) A trailer bus, as defined in Section 636.