[Tagging] Ferry lines, ways or relations?

[Dave Sutter]

I was thinking of using the ref tag as the publicly used term for the
entity. For example, there is a bus route 110 for SamTrans (San Mateo
county, California). I imagine the ref for this route is 110. There
could be some added information to specify this is a bus route for
SamTrans, as opposed to a room number in some academic building or an
exit on a freeway.

Perhaps tags such as ref:type = Bus Route, and ref:scope = SamTrans

The external database would also specify the same reference, and then
the two could be matched.

Dave