[OSM-talk] Layer transitions

[OJ W]

On Fri, Jul 31, 2009 at 7:28 AM, Harald Kleiner<e9625163 at gmx.at> wrote:
> Hi!
>
> to make my question more precise, please have a look at this tunnel that
> crosses a railway track (the railway is a subway that runs at ground level):
>
> http://www.openstreetmap.org/edit?lat=48.1325961&lon=16.3109488&zoom=19&way=29205957
>
> The tunnel tag implies layer=-1 and that leads to a junction of ways on
> different layers on both ends of the tunnel.
> On the western end of the tunnel the adjacent way ends, this should be
> no problem with the layers; on the eastern end there is a T junction.
>
> Do you think, this tunnel is OK the way it is or should someone add a
> small piece of way on layer 0 at the eastern end next to the T-junction
> to avoid a T-junction of different layers?

that's how I was doing Milton Keynes - it would be much quicker to map
if you didn't need to create 3 ways for every underpass, but it
doesn't seem technically correct to make the tunnel end at the
centreline of the road it joins with (and that would make the
rendering look weird)

http://www.openstreetmap.org/?lat=52.01666&lon=-0.744547&zoom=18&layers=B000FTF

if only there were a 'make x a bridge over y' tool in the editor that
could sort it all out for you... (splitting the way, adding the
bridge/tunnel tag to centre section, and figuring-out the minimum
layer required)