On Sat, 25 May 2019 at 08:03, Nick Bolten <nbol...@gmail.com> wrote: > What do you mean by a crossing with traffic signals AND with road markings?
> > Status quo, per the wiki: tag with crossing=traffic_signals, > hiding/erasing any information about markings that would be communicated in > other values. > > Under the new proposals: tag with crossing=marked (or > crossing:markings=yes if it ends up the proposal) and crossing:signals=yes. > Here we seem to be in fundamental disagreement. A crossing with traffic signals is a crossing with traffic signals independent of road markings: the interaction of pedestrians and traffic is determined by the status of the lights. At a crossing with only markings the interaction of pedestrians and traffic is determined by the markings. Traffic regulations for the one say that the behaviour of pedestrians and traffic is controlled by the lights; traffic regulations for the other says that the behaviour is controlled by the road markings. Please let's not drift off into semantic arguments about "controlled." Ultimately it's all about traffic regulations and ultimately laws do not control behaviour as people can, and do, break those laws. Maybe we should be talking about "passive" and "active" instead. Or signalized and unsignalized. Yes, it's of interest that in some areas a crossing controlled by lights also has road markings but, unless you can show a case that those markings make it a different type of crossing, they're cosmetic enhancements. And yes, I understand that those "cosmetic" enhancements may be important to those with visual impairment, and worth mapping for that reason, but they do not significantly change what type of crossing it is. Don't get hung up on "cosmetic" implying "trivial" or "insignificant" - I'm not saying that, I'm saying they don't change the fundamental type of crossing or the way pedestrians and traffic are supposed to interact in a given jurisdiction. I have yet to see anyone present a case where the presence or absence of road markings at a crossing controlled by traffic signals requires different behaviour by either pedestrians or traffic. Perhaps such cases exist (Poland is a possibility, awaiting clarification) but until then the defining characteristic is that the lights tell pedestrians and motorists what to do. Road markings alone is a more difficult.case because different jurisdictions assign different behaviours to them. But an important characteristic is that there are no traffic lights. In the UK, pedestrians have right of way at such crossings. In other countries they may serve purely to warn motorists to be more cautious about pedestrians attempting to cross there. It is debatable whether this should be handled as auxiliary tags (pedestrian_right_of_way=yes/no) or (as with many tags) it is something we don't map because we try to avoid mapping legislation and instead say "It's a marked (unsignalized) crossing, it's up to you to figure out what that means in this particular jurisdiction." Acid test: explain to a child how to cross the road. It is going to be along the lines of "At this type of crossing you wait for the green signal (or whatever) before you cross." and "At this type of crossing there are no lights, you behave in this (country-specific) way." I have yet to see anyone say that "At this type of crossing you wait for the green signal UNLESS there are these road markings, in which case it's completely different." If that is the case somewhere in the world then we'll have to find a way of mapping it. > > Have you ever seen a crossing with lights AND zebra stripes? Which of > the two takes > precedence? > > Neither. They are separate properties of the crossing and can communicate > different information. We can describe the number of lanes a street has as > well as it's speed limit without having to decide which takes precedent, > let's use that same idea for crossings. > Does the presence or absence of those road markings fundamentally change the interaction between pedestrian and traffic? Can we say "This crossing with lights is of type X because it has road markings and that crossing with lights is of type Y because it doesn't have road markings; the behaviour at X and Y crossings differs in these significant ways"? > However, if you include the zig-zag lines before and after the crossing > (...) > > Maybe the proposal should be updated to be even clearer: a marked crossing > is one where the pedestrian crossing space is, specifically, visibly > outlined with designated markings. > Which seems to be precisely the opposite of how most people interpret it. For me, at least, the visible outlining is cosmetic because it doesn't alter the rules of engagement between pedestrian traffic. Worth mapping for the benefit of the visually impaired, but not by redefining current usage. Current usage has marked crossings meaning "not controlled by lights." So then we need marked_and_not_controlled_by_lights and marked_but_controlled_by_lights. Which is fine, as long as you don't redefine current usage, because that would cause major problems if it went through (which it almost certainly would not). If you don't make the distinction then we have the situation that the visually impaired in the UK (and other countries) may be misled into thinking that the markings mean they have right of way at what are actually cosmetic markings at traffic lights. > > then you have the dangerous situation that the map leads people to think > that a light-controlled crossing (...) is a marked crossing (like a zebra) > where pedestrians have priority. > > With orthogonal crossing tags for markings and pedestrian signals, such a > crossing could and should be tagged as having signals. The situation > described appears to be a tagging error: someone said the crossing was > marked when it wasn't and also neglected to tag the pedestrian signals. > Situations like this, where signals get neglected, are actually easier > under the current schema due to markings being mappable from aerial imagery > while signals usually aren't. > Explain how your proposal would significantly reduce errors. Aerial mapping a new crossing with stripes is going to result in a marked crossing either way. Aerial editing an existing crossing could also result in errors either way, but possibly worse with your proposal. Currently if I edit an existing crossing because I see stripes in aerial imagery I see from the tag list that it's already been marked as having lights and would have to change that to being uncontrolled, so I do further checks (has the type of crossing changed, can light-controlled crossings have stripes in this jurisdiction). With your proposal I see a "markings" checkbox and tick it without noticing the "lights" checkbox is already ticked." > > But I suspect this is Nick;s interpretation > of what a marked crossing is - there are some marks on the road (I can't > make sense of his > proposals without that interpretation). > > My interpretation is the boringest one: a marked crossing is a marked > crossing. It's described roughly the same way by transit agencies, > Wikipedia, dictionaries, etc.: crossing with visual markings designating > the pedestrian space for crossing the street. > Wikipedia? Like https://en.wikipedia.org/wiki/Pedestrian_crossing It makes a distinction between signalized and unsignalized crossings. Which is what we have in current usage. The tag values are unclear and misleading without referring to the documentation, which is the case of many tags, but this is how most people interpret matters: crossing=traffic_signals means signalized (irrespective of road markings); crossing=uncontrolled means unsignalized. That is the current usage, and the current implication of the wiki; redefining it would cause big problems. Pelican crossings tend to have a dotted line outlining the pedestrian space > of the crossing... > It's still a signalized crossing, not an unsignalized one. Those markings are cosmetic. Outside the UK it's common to find pedestrian-signaled crossings with > virtually any marking style. Some are shown on the proposal page. > Again, those markings are cosmetic. Important to some people but do not affect the rules of interaction of the crossing. I have absolutely no objection to introducing a way of tagging cosmetic markings. I even agree with you that we should find a way of doing so. The problem comes with your apparent insistence that we redefine the current meaning of a tag. But maybe I've misunderstood what you're proposing. Redefining a tag a big problem for more than one reason. Suppose we wanted to replace landuse=grass with landcover=grass. Most of us here actually do want to do that. It would require a mass edit, and it's very hard to get consent for that even when it's a 1-for-1 substitution with no exceptions. And we have to get editor presets changed (which can be easy or impossible, depending on the views of the maintainers of the editors). And then the big problem is that the carto guys have a rule of "no aliases." They appear to be inflexible on that, even in the case of a transition like this. The old landuse=grass will continues to be rendered; the (proposed) new landcover=grass will never be rendered. That was the simple case. What if we have tags P, Q and R, where some P become X but other Ps become Y; Q and R become Z in most cases but in some cases become Y. That requires a manual edit in each and every case (assuming the proposal goes through, which is very unlikely). On 2.5 million POIs, that's not going to happen. I'm not saying I'm happy with these obstacles to cleaner, clearer tagging, because I'm not. But they're there. And I also think the distinction between signalized and unsignalized is of greater importance than whether or not a signalized crossing has some form of road markings. Come up with a way that retains current tag meanings (as commonly interpreted) and which allows cosmetic markings at signalized crossings to be mapped without any confusion between them and the markings at unsignalized crossings and I'm all for it. -- Paul
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