[Tagging] Formally informal sidewalks

[Nick Bolten]

> marc marc wrote:
>
> For wheelchair routing.
> If all crossing have a lower kerb, it is maybe enough to add
> sidewalk:both:wheelchair=yes to the street.

wheelchair=yes should be used sparingly, because it's making an editorial
decision on behalf of wheelchair users, who actually have a wide range of
accessibility preferences. Instead, we can mark potential barriers and let
them (or routing software) decide. For example, one person may consider a
rolled curb accessible (many manual wheelchair users) while another may
consider that inaccessible (certainly many powered wheelchair users). I
personally treat it as an override, such as when an implied barrier isn't
really a barrier, or when there are no obvious alternatives yet, such as
building entrances.

>> easier to add characteristics for wheelchair routing to them.
> you can add those tag to the street as documented here
> https://wiki.openstreetmap.org/wiki/Wheelchair_routing#Sidewalks
> for example I use the following tag on the street :
> kerb=raised
> sidewalk=right
> sidewalk:right:smoothness=excellent
> sidewalk:right:surface=asphalt
> sidewalk:right:tactile_paving=no
> sidewalk:right:wheelchair=yes

Yes, but that's a fairly unnatural way to describe a pedestrian way: as one
of two lanes of a street. It makes those footways invisible by default,
coded into a left/right from forward schema, leads to spatial inaccuracy
(the sidewalk is 30 meters away, there is a telephone pole blocking part of
the path...), etc. It can't properly describe crossings, since they've been
condensed into a node, but important information like length, the curbs at
each side (direction of traversal + curb type both matter), APS
directionality, etc, are all essentially linear features. Finally, it
rapidly explodes street lines with sidewalk information. If the curb is
raised, every time a driveway or alley intersects the sidewalk, the curb
changes to lowered or flush. If there are 10 driveways along a street, the
street must now be a minimum of 11 separate ways due solely to annotating
sidewalk information. Add in other features that may split the way
(smoothness, surface, barriers, street features like lanes, parking lanes,
etc) and it becomes a real maintainability nightmare.

> Guidelines for roads is very easy: split a road in 2 when you can NOT
> switch from one to the other (for example a road with a island). and
> create connection where you can switch. But do NOT cut a road into 2 if
> you switch everywhere from one to the other (for example a street with 2
> lanes must be keep as one street, not 2).
> Just do the same with the sidewalk as if the sidewalk was a lane
> reserved for pedestrians. I never see a problem with that.

Ah, but it's almost never valid to switch from a sidewalk 'lane' to a
street 'lane', or vice versa. You can cross the street, but simply walking
in the middle of it is at least unsafe, and sometimes illegal, unless it's
a pedestrian street. When pedestrian routers fall back to streets, it's
implied/hoped that you'll do the safe thing and stay out of car traffic. In
addition, most sidewalks have curbs or bollards or some other form of
barrier to some large minority of people. So, by this rule, we should
almost always draw separate pedestrian ways.

Hope this makes some sense... it feels a bit ranty.

Best,

Nick

On Sat, Jul 15, 2017 at 6:30 AM John Willis <johnw at mac.com> wrote:

>
>
> > On Jul 15, 2017, at 7:04 PM, Svavar Kjarrval <svavar at kjarrval.is> wrote:
> >
> > Just to be clear: Is it valid, in your opinion, to connect the end of a
> > footway along a street, directly to the street itself?
>
> If the street becomes the route, I say yes, especially if there is no
> reasonable barrier to prevent pedestrians from continuing.
>
> In some cases, there are barriers to stop to stop any kind or traffic. In
> other cases, one side ends and the other continues, meaning peds would
> reasonably cross there to access the other sidewalk (providing there is no
> reasonable zebra crossing nearby, a situation the occurs in my
> suburban-rural area frequently), which would the. Require an unmarked
> crossing.
>
>  But If you are walking on the sidewalk and it abruptly ends (especially
> if it makes some affordance to transition you onto the shoulder, like a
> taper or a break in the curb to allow cyclists free passage) - then by all
> means! The road is now the way you are traveling on, not the sidewalk -
> which up until 3 meters before, could have been a curb, hedge, and fence
> separated way!
>
> Javbw.
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