(b)

1. (1) When the operator has an obstructed view to the rear, self-propelled mobile equipment shall have—

   1. (i) An automatic reverse-activated signal alarm;
   2. (ii) A wheel-mounted bell alarm which sounds at least once for each three feet of reverse movement;
   3. (iii) A discriminating backup alarm that covers the area of obstructed view; or
   4. (iv) An observer to signal when it is safe to back up.
2. (2) Alarms shall be audible above the surrounding noise level.
3. (3) An automatic reverse-activated strobe light may be used at night in lieu of an audible reverse alarm.