Thanks for the note.  You're correct, I've been simply using the "does it have a dividing line" criteria for tertiary roads.  

Interestingly, I had a separate discussion with someone else about this, given that cities sometimes throw a dividing line on a road just because it is wide.  Not sure where that went; I don't know how to track changeset discussions via the web site.

While I'm not totally happy about moving the criteria from objective to subjective, I agree it makes more sense to provide a way of describing a road's connectivity than looking for lanes.

Anyway, I'll try to use more lane_markings=yes.  I'm not sure about adding the corresponding lanes=2; better data but it kind of kills the joy.