companies hauling tankers seem to be the ones leading the way on air disc brakes as wieght is critical and airdisc system is lighter. I would think there hass to be some type of back up to automatically apply the brakes in event of loss or low air situation. If you have a fuel depot or large tank fleet nearby you might try to go by and talk to drivers or fleet maintence guys. Failing that go to leehi truckstop rt 11, white's or the wilco on exit 205. wilco might be your best bet they go thru a lot of fuel and proably have several fuel drops a day and they have a dedicated fleet of trucks so you could proably catch a driver there.