OOSC, Part II, Item 1. Brake Systems, l. Tractor Protection System

I believe that there is one option missing in the OOS part 2 item 1 L Tractor protection system. I was supervising a level 1 inspection, the officer followed step 32 Tractor protection system check properly, so did the driver, the trailer air supply (red) valve popped between 50 and 60 PSI (gauge accuracy). We noticed that the Parking brake (yellow) valve had also popped. We conducted the test 3, more times to ensure we did not miss a driver action. We also ensured the parking brakes were fully applied when that happened and they did.

I thought of the purpose of the tractor protection system was to ensure that, in the event of a serious air leak in the pneumatic system of the towed vehicle, the driver could reach the curb because the towing unit does not have the emergency brakes applied. That cannot happen in the situation i experienced. I checked and FMVSS 121 states S5.1.3Towing vehicle protection system. If the vehicle is intended to tow another vehicle equipped with air brakes, a system to protect the air pressure in the towing vehicle from the effects of a loss of air pressure in the towed vehicle. So the tractor protection system did what it is required to do according to FMVSS

First could we check with NHTSA to ensure that the wording they use reflects what they want compared with to the situation I experienced. Second request, add a 3. in the tractor protection system OOS: The parking brake control valve of the towing unit shall not close before completion of the test.