chargers

Where a vehicle can charge, in declaration order.

Ordinary places in the layout -- an intersection, a station alias, a named point -- because a charger is a place a vehicle drives to and nothing else. Nothing in the space layer changes to have one, and a charger on a spur behaves like any other spur: one vehicle at a time, with the rest queueing on the approach.

Fleet-wide rather than per vehicle, since a charger belongs to the layout. A fleet whose vehicles take different chargers says so through its disposition policies.