Minx slowed. Something heavy banged and something metallic squealed. A door swung open. They stepped out onto a concrete safety walk that ran along one side of an underground roadway. Monk couldn't recall having ever seen this part of the transitways before. The roadway, only two lanes wide and divided by white dashes, extended off in both directions for a few hundred meters before curving out of sight. The pavement looked really clean. No litter anywhere.