Into the Pitt

There was a gate back there on the main road into the Pitt, and while it had a sensible lock and sensible razor wire, the lock was on the outside. A certain amount of diligent scouting uncovered why: about a quarter of a mile past the gate, there was a ruined building that housed a population of... well. The raiders who lived in Springdale School and hung the corpses of their victims from hooks as a lighthearted interior decorative touch would've taken one look at the people in that ruined building and gone 'oo, what nasty people'. And the boys wrecked on the island in Lord of the Flies would've backed away from the sight and taken a good long look at their lives and their choices, frankly.

Not that anyone wants to be locked into the same set of walls as people like that, but the building in question was on one bank of the Monongahela River, and the looming bulk of what had once been Pittsburgh and is now marked only with the sign 'Welcome To The Pitt' is on the other. The only way across is via a suspension bridge mostly blocked by the bulk of rusting, rotting pre-War cars, and guarded by multiple snipers up on each of the bridge's towers.

The Pitt is a city of slaves. If the slaves who try to escape somehow manage to make it past the snipers, that gate's there to make sure that not only do the slaves not get away, they're pinned in an almost ideal location for either the savages in that building to come and drag them away, or for their masters to come and pick them up without a fight.

That's why the lock is on the outside.