Q is used on what they call a quint. its just a fire engine equipped with a ladder
prior AF Crash Rescue and the Q is identifying that that is a Quint. Dual Purpose Engine and a Ladder.
Quick attack vehicles are generally small pickups or light trucks with limited water/foam to get a quick hit on the fire.
The Q on that truck is saying it is a quint/ dual purpose. I have friends that were stationed there. Im prior AF Crash Rescue