Intersection Zone
The space of a junction, held by one transporter at a time.
An intersection is space as well as a place. Treating it as a zone is what makes spur semantics expressible at all: a transporter sent to the end of a dead end has to keep hold of the mouth in order to get back out, and "the mouth" is this zone.
Its length defaults to zero, the usual modelling assumption that a junction is a point. A zero length does not make the zone free to share; it remains exclusive.
Parameters
id
index within the network's zone list
intersection
the junction whose space this is
length
the distance to cross the junction, zero or more
velocity Factor
multiplies transporter velocity while crossing, strictly positive