LoadedFirstZoneContentionRule

Gives the zone to a transporter carrying something, in preference to an empty one, and otherwise to whoever has waited longest.

A loaded transporter is holding up a job, while an empty one is only repositioning, so letting the loaded one through first tends to shorten the time entities spend in the system. It can starve an empty transporter on a busy path, which is a real risk rather than a theoretical one and is why it is not the default.