R7

R7 / Generalization

Conduit is a Paired Conduit or Unpaired Conduit

A Conduit is either used as part of a two-way pair, in which case it is Paired, or it defines one-way traffic in which a single, unpaired Conduit suffices.

Comment: This works nicely until we consider cases where one pair of Conduits is sandwiched inside of another Pair as happens in freeway interchange feeders. The “Toronto Basketweave" is an extreme case in point. But we need only look at the I280/SR-1 interchange in South San Francisco, CA, USA for an example. The definitions may still hold if we have a good model that explains freeway feeder patterns, which we do not currently have. All that said, we need a clear set of rules since the idea of just grouping Conduits arbitrarily is certainly not a solution that accurately characterizes the real world!

Formalization

Paired Conduit.(Road segment, Orientation) -> Conduit.(Road segment, Role)
Unpaired Conduit.Road segment -> Conduit.Road segment