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.