Wouldn't tagging toll information for and only for the tunnel area be "consequential mapping" as well, as you are basing it on whether "some other feature" (in the case, tunnel area) exists? And as I said, what will do if a non-tunnel area is tolled?

Imo whether a road is tolled or not is a property of its own, and not a consequence of anything. E.g. `lit=` is entirely dependent on the existence of street lamps ("some other feature"), but tagging `lit=` wouldn't be "consequential mapping" because `lit=` is a property of the road.

> Upon review, I notice this case is logically equivalent to the "extend motorway" rule, which I personally dislike.

I don't see a problem with the rule. It should be agreed upon that `highway=` is for functional classification, and it doesn't make sense for a road to suddenly change importance for no reason. Furthermore, `highway=motorway` is a legal class, so all roads not accessible without `=motorway` will inherit the same restrictions/access control as you can't turn back. I.e. `=motorway` should not start without an exit towards a non-`=motorway`, and should not end without an entrance from non-`motorway` (which is why I personally disagree with e.g. https://www.openstreetmap.org/changeset/168099947)

Similarly for tolls, if a road can't be accessed without also using a toll road, then you must pay a toll to use it. E.g. https://www.openstreetmap.org/way/47071903 is `toll=yes` because it only leads to Tai Lam Tunnel (tolled), and indeed irl there are "Toll Area" and toll schedule signs to let drivers know they are at a "point of no turning back" towards a toll road, and they must pay a toll if they wish to proceed.

Also, as I said, if you don't extend `toll=`, then when can you use it? Inside tunnel area wouldn't work as I mentioned above. Is it only for `barrier=toll_booth` or `highway=toll_gantry`? But don't those already imply `toll=yes`, making it a "consequential mapping" by your standards? When do you propose to use `toll=`?