I'd be more interested in including only where I actually have to pay a toll to travel. So the NY Thruway and Mass Pike would not be fully clinched by the toll_roads user.
I agree.
For the beltways, are we thinking beltways named as such or any that functionally behave as beltways? I don't have a preference other than for some consistency.
I've only considered ones that might be considered such from the road (ie signs saying 'ring', 'loop'*, 'belt', directions of inner/outer, etc) rather than a map. But I'd be open to a different definition (mine, for instance, doesn't require a full loop) - consistency is, I agree, what matters here.
The latter ends up rather vague whereby any loop of roads might count. Paris'
Grand Contournement is (I believe) a somewhat deliberate loop of tangential roads rather . But if I do a C-shape a similar distance to London (A27-M27-M3-A34-A43-A45-A14), because some roadgeeks consider it to be a similar concept, then we're clutching at straws here. And if I invented the same sort of thing for Chicago with I-74-I-39-I-43 then the user would be pointless.
*This one, obviously, needs to be a bit subjective, to avoid business loop type roads.