[Tagging] Sidewalk Tagging for Routing

Clifford Snow clifford at snowandsnow.us
Wed Nov 25 00:51:30 UTC 2015


On Tue, Nov 24, 2015 at 4:14 PM, Philip Barnes <phil at trigpoint.me.uk> wrote:

> They are not matching reality, can cause long detours and poor routing
> unless the mapper provides a lot of connections to the road. Remember
> normal pedestrians can cross wherever they want.
>

That is true, but what we want to give someone in a wheelchair is a route
that they can safely take. So at a minimum, the way must be connect, where
appropriate, at intersections and other recognized crossings.  A recognized
crossing would be one with markings for pedestrians or from local
knowledge, that it is safe to cross the street.

>
>

> There is also the simple rendering issue, roads are already wide and
> are very close or clipping buildings. The sidewalk if mapped in
> position is likely to be hidden under the road.
>

I'm hoping that a wheelchair map would draw the sidewalks and minimize the
streets.  That is a rendering issue. As we like to say, don't map for the
renderer.


> > Setting aside the newbie friendly issue, how do you map a crosswalk
> > in the middle of a street?
> Add a node where the drop kerb is and map which side it belongs to.
>

If I understand correctly, at a street crossing, the tags would be

highway=crossing
kerb:(left/right/both)=lowered

>
>
> > How do you map kerb slopes when the the slope is in the corner the
> > intersection?
> I assume by kerb slope you mean a drop kerb? They are never in the
> corner. Remember the way, when editing, represents the centreline so
> they are a few metres into the joining street. This also give turning
> vehicles space to stop for pedestrians.
>

Unfortunately, at least around here, they often place the wheelchair ramp
in the corner. My guess is it cost less money. As I said earlier, using the
corner results in 4 instead of 8 ramps on a typical intersection. A picture
of one of these ramps might help. I'll see if I can dig one up.

It wouldn't be accurate, but using the same logic as above,
(highway=crossing, kerb:(left/right/both)=lowered) would work.

>From taginfo, kerb=lowered seems to be the most popular usage and is
documented [1]. sidewalk:right:sloped_curb:end [2] is also documented but
has limited usage.

[1] https://wiki.openstreetmap.org/wiki/Wheelchair_routing
[2] https://wiki.openstreetmap.org/wiki/Proposed_features/kerb

You have convinced me that the attribute method is optimal.

Thanks,
Clifford

-- 
@osm_seattle
osm_seattle.snowandsnow.us
OpenStreetMap: Maps with a human touch
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