Park/Trailer valves

[Chamberpains]

Yes. And I can also say that its only been the last couple years that DOT road side checks have been checking for this operation more intensely. NY made me pull my trailer air line while the brakes were released, MD made me bleed the system down by pumping the brake pedal till they both popped and KS made me pull just the tractor brake to see if the trailer followed. And this was in the last 2 years of Inspections. I never had anything but a bleed down test for the low air alarm from 2005 till 2016 so when they started testing this I was quite surprised they did it and surprised my old valve set passed!! Hahaha.

The law is sub section 393.43
Here is a link to an article that goes into some detail about it spawned by a run away truck. The pop out law appears to have been writen in 1988.
http://part380.com/blog/tag/protection-v...%A7393-43/