the 20 min audio clip of the run away train is interesting to listen to... i moved units around a few times [like to get a smokey one out of the shop quickly] that have been low on air. not a fun feeling when you want to stop and there is nothing there when you apply the brakes. we usually charge the system to 80-90psi with shop air [60 minimum needed i feel to start moving] but that takes time. the few times i've moved with low air, i leave the hand brake applied and over power it with the throttle so i've got something wanting to slow me down once i get out side the door.