[Tagging] Feature Proposal - RFC (etc) for crossing:signals

[Nick Bolten]

> However, it seems odd to "demote" traffic signals to a sub-tag when their
presence or absence is perhaps the biggest influence on the crossing's
overall character.

I agree that it's not ideal to have to make these kinds of choices about
"demoting". In case it's helpful, this is my original rationale:

1) To have properly orthogonal values for the crossing key, it should
describe one category of things, like markings or signals. This means
"demoting" all but one feature to other tags (hopefully namespaced) like
crossing:signals. Imagine if highway=primary originally implied 4 lanes as
well as "major, separated high-speed street" and only later did we have to
separate out highway=primary from lanes=4. We agree on this, just thought
it was an important point.

2) Which category should be used as the primary value of crossing? I went
with the marking because it is, by far, the most-tagged value:
uncontrolled/zebra/marked/unmarked account for 3 times as many tags as
traffic_signals.

> In comparison, it seems somewhat less important whether a signalled
crossing also has painted markings on the road. So I would suggest using a
separate tag for the markings instead. We need a tag for the _type_ of the
markings anyway (as different patterns for marked crossings can have
entirely different legal meanings in some jurisdictions), and we can use
that same tag for presence/absence by also allowing yes/no values.

Would it be fair to say you're suggesting something along the lines of
crossing:marking=*, where * can be yes, no, or a marking type? You make a
good point about the simplicity of avoiding a subtag for markings.

Aside from frequency of tagging, the biggest reason I've prioritized
markings as the primary value is that marked crossings are starkly
different from unmarked ones from many different perspectives:

- Unmarked crossings are abstract "fictions" representing where an
individual might cross the street, marked crossings are identifiable from
imagery.
- Because unmarked crossings are "fictions", they are only suggested places
to cross, according to the mapper. In contrast, marked crossings are
"official".
- Marked crossings confer safety and right-of-way information to both
pedestrian and street traffic: this is a place where pedestrians can cross,
so watch out.
- Marked crossings are one of the few pedestrian spaces that can be
straightforwardly considered as a linear feature: it connects spaces across
a street.
- Marked crossings tend to have legal implications, as you note.

Thus, when someone asks me, "what type of crossing is this?", my gut
reaction is to say "a crosswalk" or "not marked", potentially followed up
by a marking type if applicable. A marked crosswalk is a real,
"on-the-ground" thing whereas unmarked is a workaround for needing to
representing and use 2D spaces as lines.

I'd be curious to find some survey data regarding the importance of
pedestrian features that included crosswalks and signals. I could've sworn
I knew of one, but am having trouble finding it.

Best,

Nick

On Tue, May 7, 2019 at 3:08 PM Tobias Knerr <osm at tobias-knerr.de> wrote:

> On 07.05.19 23:08, Nick Bolten wrote:
> > This proposal suggests the deprecation of crossing=traffic_signals and
> > replacing it with crossing:signals=yes, i.e. placing pedestrian
> > signalization on a dedicated tag that is separate from crossing=* values.
>
> I agree with separating orthogonal characteristics of crossings into
> different tags. A single tag cannot easily express both the presence of
> traffic signs and the presence of markings.
>
> However, it seems odd to "demote" traffic signals to a sub-tag when
> their presence or absence is perhaps the biggest influence on the
> crossing's overall character.
>
> In comparison, it seems somewhat less important whether a signalled
> crossing also has painted markings on the road. So I would suggest using
> a separate tag for the markings instead. We need a tag for the _type_ of
> the markings anyway (as different patterns for marked crossings can have
> entirely different legal meanings in some jurisdictions), and we can use
> that same tag for presence/absence by also allowing yes/no values.
>
> Tobias
>
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