41-6a-1623. Braking systems required -- Adoption of performance requirements by department.
(1) A motor vehicle and a combination of vehicles shall have a service braking system which will stop the motor vehicle or combination of vehicles within:
(a) 40 feet from an initial speed of 20 miles per hour on a level, dry, smooth, hard surface; or
(b) a shorter distance as may be specified by the department in accordance with federal standards.
(2) A motor vehicle and a combination of vehicles shall have a parking brake system:
(a) adequate to hold the motor vehicle or combination of vehicles on any grade on which it is operated under all conditions of loading on a surface free from snow, ice or loose material; or
(b) which complies with performance standards issued by the department in accordance with federal standards.
(3) In addition to the requirements of Subsections (1) and (2), if necessary for safe operation, the department may by rule require additional braking systems in accordance with federal standards.
I guess it comes down to the definition of 'system', do they have to be separate. You'll see the state law defers to federal standards, which I can almost guarantee require them to be completely separate standalone systems to create redundancy.
Federal Park Brake Standard:
S5.2 Parking Brake System. Each vehicle shall be manufactured with a parking brake system of a friction type with a solely mechanical means to retain engagement, which shall under the conditions of S6, when tested according to the procedures specified in S7, meet the requirements specified in S5.2.1, S5.2.2, or S5.2.3 as appropriate, with the system engaged-