An “axle” is a structure or portion of a structure consisting of one or more shafts, spindles, or bearings in the same vertical transverse plane by means of which, in conjunction with wheels mounted on said shafts, spindles, or bearings, a portion of the weight of a vehicle and its load, if any, is continuously transmitted to the roadway when the vehicle is in motion.
(Enacted by Stats. 1959, Ch. 3.)