Most likly a "staff" car. This vehicle is commonly used in the U.S. and I would assume Canada for the "training chief" or someone who might be required to carry extra equipment (spare air bottles or training props) from station to station. Odds are the "car 5" designation is more of "who" the vehicle is used by..ie car 1 might be the Fire Chief, car 2 might be the chief of operations and so on. Just guessing but that is how it is in the U.S. Hope this helps.
Added by Lambert Arnaud on 30 July 2010.