Question A low air pressure warning signal: Answers Is not recommended on vehicles with air brakes. Is required on vehicles with air brakes. Is optional on vehicles with air brakes. Explanation Any vehicle with air brakes must be equipped with a low air pressure warning signal. This questions appears in the following tests: Arkansas Air Brakes Connecticut Air Brakes Idaho Class A Knowledge Test Kentucky Double Kentucky Air Brakes Kentucky Air Brakes Maryland Air Brakes Mississippi Air Brakes Missouri Class A Knowledge Test Missouri Air Brakes Nebraska Air Brakes Nevada Air Brakes New Mexico Air Brakes Oklahoma Air Brakes Oklahoma Air Brakes South Dakota Class A Knowledge Test Utah Air Brakes Vermont Air Brakes Virginia Double