Sign requirements

(a) A portable sign shall be placed at a height of at least four (4) feet above ground level and display the words "CARRYING SCHOOL CHILDREN" in black lettering at least three (3) inches high on a yellow background. The lettering may be painted on the sign, or the lettering may be applied to the sign by a permanent decal. The words "STOP" or "STOP ON SIGNAL" shall not be used on a portable sign. A portable sign shall not be mounted below the windshield of a vehicle, or on the hood or the rear of a vehicle, except that to provide the required visibility required by Section 14-280-2 (a) a second portable sign may be mounted securely on the rear of a vehicle if the sign does not pose a danger to persons or property, or does not interfere with the driver's vision or with ingress or egress to the vehicle. (b) When a motor vehicle is being used for purposes other than transporting school children, portable sign(s) shall be removed, completely covered, folded or otherwise concealed so that the words displayed thereon are not visible to the operators of other vehicles.