Last time in T5 there were two queues in the "Fast Track", each with 14-15 pax. Looking left, the ordinary tracks had 7-9 pax each. Excused myself to others in my queue for turning back. Despite time taken to change lanes, I cleared security when the 4 pax in front of me in original track still waited for their turn.

At that time I re-evaluated the meaning of Fast Track:

It's the time-consuming place making you loose weight to abstain from all food, or to eat only sparingly or of certain kinds of food, esp. as a religious observance.

Or just the place to get stuck, firmly fixed in place; not easily moved; securely attached.

held or caught firmly, so as to be unable to escape or be extricated: an animal fast in a trap.

firmly tied, as a knot.

closed and made secure, as a door, gate, or shutter.

Lots of other plausible definitions in this link

http://dictionary.reference.com/browse/fast