Sec. 604.2. [Speed limits.]

(a) The limits specified or established herein, except where a special hazard exists that requires lower speed for compliance with the preceding section, shall be maximum lawful speeds and no person shall drive a vehicle on the vehicular crossing at a speed in excess of such maximum limits.

(1) Passenger cars—40 m.p.h.

(2) Other vehicles—30 m.p.h.

(3) In truck yards and trailer areas—10 m.p.h., unless conditions as herein-above stated are such that safety requires a speed of less than 10 m.p.h.

(b) Nothing herein contained shall be construed to apply to police and fire department vehicles, ambulances and to other emergency vehicles.