[OSM-talk] Layer transitions

[Lauri Kytömaa]

Lambert Carsten wrote:
>sense. Even though the smaller road ends at the edge of the larger road
>not the middle of the road.

Inside the crossing area the roads overlap, neither ends there - you're
on both roads. But you're not on the bridge that starts only several
meters away - or inches away if you're already moving towards the
bridge.

Taking the canal bridges mentioned previously: if you draw the
riverbanks/canal edges, it has been the recommendation (I'd have to dig
the talk list archives for that) also that the bridge=yes starts and
ends at the points where one can get under the bridge - at the water's
edge, meters away from the ways marking the roads running parallel to
the canal.

One thing about the same layer check occurs sometimes: a motorway link 
road joins the motorway right at the point where the bridge starts: most 
notably the case where the road markings indicate three lanes on the 
bridge and only two (+1 approaching but still separate) up to the exact 
point where the bridge starts. We can make the connected node something 
other than the point where the lanes come into contact (the acceleration 
lane's hundreds of meters long anyway, but that would need some kind of a 
note to be consistent - at least once more people start to get to that 
level of detail.

-- 
Alv