[OSM-talk-be] sidewalk as ways or tags

[Ben Laenen]

Renaud MICHEL wrote:
> Hello
> 
> I have recently had a small edit war with user nondidju regarding my
> tracing of sidewalks as separate ways, see
> http://www.openstreetmap.org/browse/changeset/7461451
> http://www.openstreetmap.org/browse/changeset/7528743

This is the whole "tag cycleways as ways or tags" discussion all over again.

Simply put: simple sidewalks next to a road: don't map as separate ways. Start 
doing this when we map ways as areas maybe...

If a footpath or cycleway is really a separate path which isn't just sitting 
next to the road, then you can draw them as ways. Paths like these have often 
grass or other barriers between them and the road itself.

Example of a good place to draw separate cycleways and footways: 
http://osm.org/go/0Ekgh7qB5--

Example of a bad place to draw separate footways: almost all residential roads 
in a city.

Whether the examples you give are good or bad is up to you to decide; I'm not 
familiar with those places.

> He argues that the mapnik rendering of this show how irrationnal it is
> (which is a personnal preference on which I differ) and that those should
> be tagged on the main way.
> I personnally think that it is more topologically correct, having a
> parallel footway (where there exists ont) and foot=no on the main road, as
> on important roads you may not cross anywhere, but only where a crossing
> exists, so a separate way allow for correct routing for pedestrians.

Can you show an example where this is the case, where you're not allowed to 
cross a road, but are allowed to walk on sidewalks next to it? I may have 
missed something, but I think the traffic code simply doesn't make it possible 
to have such a situation. Except when there really is a separate path next to 
the road, in which case the two just happen to be parallel and in which case 
drawing the footpaths as separate ways is the only logical option. And in 
which case you should really reconsider whether "footway" is the right 
designation.

Also, only put a tag like foot=no on the road when there are signs explicitly 
forbidding pedestrians on the road. Without such a sign, the road allows 
pedestrians walking along it (on the sidewalk or footway if there is one which 
is part of the road, or on the road itself otherwise), and crossing it 
anywhere they like, even if it would not be wise to do so. Because without the 
sign, pedestrians can still walk on the road if the sidewalk and verges happen 
to be blocked.


> As an
> example, on this way
> http://www.openstreetmap.org/browse/way/57687924
> you may simply not cross the road between the bridges.
> (I don't create parallel footways for every road, only those where I
> consider it unwise to cross anywhere)

"unwise" is a very subjective word. Tag the reality, nothing more.

> Another example
> http://osm.org/go/0EqqLNEt0--
> Here you may not cross the road on sides of bridge "Albert 1er", you may
> either take the tunnel on the right side, or go to the traffic signal on
> the left.
> 
> From a recent discussion on newbies@
> http://lists.openstreetmap.org/pipermail/newbies/2011-March/006340.html
> it seems the recommanded way to tag those is to use a footway tag on the
> main road, but with this, routing engines have to do a preprossing to
> recreate the topologically correct ways, or have a more complex algorithm
> taking into account on which side of the road you are walking and where you
> way cross.

That's a non-issue. These routers are getting better everyday. Don't start 
modifying data to help them do something now which they might do themselves 
tomorrow.

If you're really not allowed to cross a road, then the road is either a 
motorway, motorroad or has a sign forbidding access to pedestrians. And in 
these cases paths next to it are separate from the road and need their own 
ways.

We're of course still left with the issue of linking footways and cycleways to 
a road so a router can tell whether a pedestrian has to follow the path next 
to it (when these paths are part of the road) or not (when the path is a 
separate road itself), but then we probably enter the realm of the previous 
discussion on this list: street relations...

Greetings
Ben