# [Tagging] Formally informal sidewalks

Nick Bolten nbolten at gmail.com
Sat Jul 15 23:29:28 UTC 2017

```> no, it isn't a pedestrian way, it is a street with sidewalk, it is not the
same for routing.

There is certainly a dedicated pedestrian (and maybe cycling) way there:
the sidewalk. If the sidewalk:right* keys are meant to only describe
features of the street, then they are complementary to, rather than an
alternative to, highway=footway, footway=sidewalk.

> well... every way is a spatial inaccuracy because we use a way in stead of
an area..  (...)

For sure! There's always a sacrifice of spatial accuracy in mapping
abstractions. But there's also a point where they get stretched too far -
and in these cases, we're trying to shoehorn separated pedestrian ways and
features encountered along them into street centerlines, with all the
downsides and awkwardness I mentioned.

> Or not, the street and the sidewalk do not change often here (> 10
years), the sidewalk is often the same type/surface/kerb ... for the whole
street.

Sure, but more data gets added as people map more features. And I
underestimated the number of segments: a block with 10 driveways would
actually need to be split into 10 lowered/flush curb sections and 11 raised
sections, for a minimum of 21 segments for a single block. This is ignoring
curb ramps (each adds 2 more), and other features meant to split road ways,
like turn lanes, lane numbers, parking lanes, etc. And then someone comes
along and wants to say, 'the surface of the sidewalk from here to here is
asphalt' and sees a bajillion segments. This is with the additional loss of
specificity and visibility of the features, and the only gain is that a
pedestrian network is shoehorned into a street network.

> Before advising people to describe as separate path when this is not the casethe
routing must first understand that our 2 way are a sidewalk connected to a
street.If not, you break the routing and the only advantage seems to move
sidewalk 3m away.

Not sure if I understand what you mean, I'm not sure how this breaks
routing.

> Read me again, I did not say you can walk on the road if a sidewalk
exist. I stated the rule used to know when a road must be single or
splited. (...)

I think there might be a misunderstanding, because I didn't say otherwise...

> By keeping this rule for sidewalks, we avoid a lot of routing problem.

But I'm pointing out that by that same rule, sidewalks should usually be
split a road in 2 when you can NOT switch from one to the other (for
example a road with a island)."

The trouble is that unlike roads, where vehicular access falls into very
few category restrictions, pedestrians have a huge diversity of
restrictions. So for many (10-20% of the population), you "can NOT switch"
from the sidewalk to the street due to things like curbs or bollards or
safety concerns.

And finally, for routing to actually handle street crossings as nodes and
things like driveways, they need to essentially recreate the topology of
separated sidewalks anyways (and none do this). These features are actually
mostly ignored for pedestrian routers and used instead for routing
motorized vehicles.

But we're getting a bit off-topic. In terms of the original question, I
think using highway=forward, footway=crossway is the least-bad option for
making sure separate sidewalk ways are well-connected to the street grid,
including when sidewalks terminate.

Best,

Nick

On Sat, Jul 15, 2017 at 1:53 PM Martin Koppenhoefer <dieterdreist at gmail.com>
wrote:

>
>
> sent from a phone
>
> > On 15. Jul 2017, at 08:13, Marc Gemis <marc.gemis at gmail.com> wrote:
> >
> > I think adding sidewalks might benefit pedestrian routing
>
>
> adding driveways benefits pedestrian routing as well, because you can
> consider all those little crossings as potentially dangerous, and route
> people (e.g. kids) through places with fewer driveway crossings. Plus you
> see for the gates whether cars can pass.
>
> Admittedly, it really depends on the situation whether I'd map all of them
> or refrain for the moment because it seems too tedious and too little to
> gain.
>
> Cheers,
> Martin
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