collect
Whether the space layer registers a response per link.
Off by default, because a large network would otherwise put a row on every report and in every output database for every aisle in it. The passive subsystem takes this as a constructor argument; here it is a property, settable up to the moment the model runs, and switching it off again takes the responses back out.
A model that wants to know where its congestion is has no other way to ask. Fleet-level rows say how much blocking there was; these say which aisles produced it.