Wis. Admin. Code Trans § Trans 309.10
An ambulance shall have 2 unobstructed door openings in addition to the doors for the driver cab compartment. There shall be at least one door opening on the right forward side and a single door or double doors at the rear of the patient compartment. A forward hinged single door, double doors or a sliding type door shall have a minimum right side door opening of 30 inches in width, and 54 inches in height for Types I, I-AD, III and III-AD ambulances and 42 inches in height for Type II ambulances. The opening shall provide clearance to allow access and removal of a patient strapped to a long spine board. Single or double rear loading doors shall cover a clear opening of not less than 46 inches in height and 44 inches in width for Types I, I-AD, III and III-AD ambulances, and the manufacturer's standard for Type II ambulances. The ambulance body doors shall be equipped with not less than 250 square inches of safety glass area per door. Doors shall be designed for easy release from both the interior and exterior of the ambulance, but an accidental opening shall be prevented by an interlocking system that functions even when doors are not completely closed. Each door shall have effective compression or overlapping seals to prevent the entry of dust, water and air. Doors may contain recessed compartments to the interior for storage of supplies and devices.
Wis. Admin. Code Department of Transportation Trans 309.10