[Accessibility] Question about accessibility tagging, key:incline, and sidewalks

[Stefan Hahmann]

Hi Charles,

I could reply from the perspective of developing a routing system (we 
are developing http://openrouteservice.org that currently contains a 
beta version of a wheelchair routing profile):

For implementing routing algorithms it is generally easier, if the 
sidewalks are separate geometries, since then the routing algorithm can 
directly handle them as separate features.

However, since there is a considerable share of sidewalks that is only 
attached to the respective streets as metainformation, we have to deal 
with these situations anyway and derive "virtual" lines within the 
routing engine. There is a good article about the concept how to derive 
these virtual lines from the sidewalk tags in the OSM Wiki: 
http://wiki.openstreetmap.org/wiki/User:Maxbe/B%C3%BCrgersteigrouting
Unfortunately, this is only available in German language, but since 
there are lots of illustrations, I think the concept gets a little bit 
clear even without reading the text.

When to use separate lines and when to use metainformation attached to 
the roads to me seems to be very idiosyncratic, i.e. it depends on the 
preferences of the local mappers, if not even of the individual mappers.

Nevertheless, the distinctions criterion that you describe (whether 
sidewalks are *directly* attached to the road or whether there is any 
separating feature) makes sense to me.

For the key incline - I think, it is reasonable to assume that an 
attached sidewalk has basically the same incline like the road (at least 
within the accuracy needed 1% difference is not important here). 
However, this does not hold true for surface and smoothess, which can be 
very different between road and sidewalk. There it makes sense to 
specify them for the sidewalks separately. Tagging schemes like 
described here: 
http://wiki.openstreetmap.org/wiki/Wheelchair_routing#Sidewalks may be 
perceived as very complicated by potential mappers. My personal feeling 
that it would be little bit easier to attach sidewalk relatied 
information (e.g. surface/smooth) to a separate lines, since complicate 
constructs, such as sidewalk:left:surface 
<http://wiki.openstreetmap.org/w/index.php?title=Key:sidewalk:left:surface&action=edit&redlink=1> 
could be avoided.

Best,
Stefan.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/accessibility/attachments/20160125/e5d23323/attachment.html>