Ariz. Rev. Stat. § 28-337 – High occupancy vehicle lane; lane degradation; priority use

A. In accordance with 23 United States Code section 166, the department shall develop procedures to monitor the impact that single occupancy vehicles authorized under sections 28-2416 and 28-2416.01 have on the operation of the high occupancy vehicle lanes.
B. If a high occupancy vehicle lane becomes degraded due to the authorization of single occupancy vehicles authorized under sections 28-2416 and 28-2416.01, use of the lane is restricted to the following vehicles in the following priority:
1. 1. Passenger vehicles with two or more occupants, including the driver.
2. 2. Public transit buses.
3. 3. Buses with two or more occupants, including the driver.
4. 4. Motorcycles.
5. 5. Alternative fuel vehicles.
6. 6. Low emission and energy efficient vehicles.
C. The department shall limit use to vehicles in the priority order prescribed in subsection B of this section and shall maintain those restrictions while the lane or portion of the lane remains degraded.
D. For the purposes of this section, a high occupancy vehicle lane is degraded if vehicles operating on the facility, or portions of the facility, are failing to maintain a speed of forty-five miles per hour or greater ninety per cent of the time over a consecutive one hundred eighty day period during morning and evening weekday peak hour periods.