[Tagging] How to tag correct number of lanes for freeway on/off ramps?

[Matthew Woehlke]

Consider https://www.openstreetmap.org/#map=17/42.85888/-73.77169. As I 
write this, I-87 is annotated as having 3 lanes south of the on/off 
ramps (south of 146). However, the off ramp starts all the way back at 
the Sitterly Road overpass, and the on ramp doesn't fully merge until 
just before the emergency vehicle turn-around only slightly north of 
said overpass. Accordingly, there are actually four lanes for these 
stretches.

What is the correct way to model this?

I'm thinking, for the off ramp, the `highway:motorway_junction` should 
be pushed back, the relevant segment made 4-lane, and possibly get 
`change:lanes=yes|yes|yes|no`; the location where the ramp splits from 
the freeway should be left as-is (currently where the ramp actually 
separates from the freeway). For the on ramp, make the relevant segment 
4-lane with `change:lanes=yes|yes|not_right|yes`. Is that the sensible 
thing to do, or is there another way?

-- 
Matthew