Silly me, I said that valve was by the driver's knee,
not his foot.
Glad you found it.
May I suggest that you sit down in a chair that does not move for
a minute and just kinda catch your breath?
Seriously, if you were a new truck driver at My Place Of Gainful
Employment, I'd now take you for a walk around the yard and just
casually look at all the wrecked trucks back there. And just as casually
mention how each bang-up happened.
In your case, I'd worry most about the rear overhang. It turns right when
you turn left! Stay well clear of the fuel pumps.
I'm on my way to work, so I "had to".