Hi all,
We've been drafting a longer response that we wanted to share with everyone to give more context (for those also following the import list-serve, there is a separate post there that goes through import-specific challenges). Firstly, thank you to everyone for engaging with such vigorous discussion! We’ve learned a huge amount about the weaknesses and strengths of our current proposal. We think it would be helpful to talk about our motivations in posting this schema, to give the points we’re making some context. We have started this project with the goal of making sidewalks in OSM more useful for the greater community, particularly for people with limited mobility. With its principles of openness and inclusion, OSM is uniquely positioned to adopt a data model that can make a big difference for people who use wheelchairs, crutches, or otherwise have difficulties walking, while also improving the data in the map. We also see this as an opportunity to get more people mapping and more data about pedestrian ways into OSM, as the current state of sidewalk coverage is very poor (and is inconsistently tagged) outside of a few notable cases. One thing that we didn’t make very clear in our initial proposal is that it is primarily about suggesting standard practices for using existing tags to describe sidewalks. Almost every tag or feature listed in the Pedestrian Layer section (http://wiki.openstreetmap.org/wiki/Proposed_features/sidewa lk_schema#Pedestrian_Layer) is already described in other sections of the wiki with some description of their semantics, but it is difficult to get a coherent picture of ‘this is the way to map pedestrian ways’ because they are distributed in different tagging discussions (sometimes in conflicting ways). Almost all of the suggested tagging conventions are in use in some fashion or another. For example, Ilya Zverev pointed out that it’s a common practice to annotate sidewalks as separate ways in Russia. For another great example of the potential for impact, the wiki user Species (very helpful and active on the Talk page!) has mapped sidewalks as separate ways in Graz, Austria, and has wheelchair routing working with an OSRM profile: http://mm.linuxtage.at/osm/routing/wheelchair-electro/?z=19&; center=47.075926%2C15.440831&loc=47.076457%2C15.441271&loc= 47.075407%2C15.440565. And even in locations making heavy use of sidewalk=* on streets, you will find separately-mapped sidewalks due to important discrepancies between street shape and sidewalk shape or in order to map features that are between the sidewalk and the street. So a point we’d like to make is that many of the concerns raised don’t just apply to a proposal for tagging in the future - they apply to pedestrian ways that are already mapped as well. It would be interesting to see examples of how different regions have coped with the issues raised here (like crossing streets anywhere), as there may be multiple strategies that already handle that situation. The introduction to the proposal has been reworded to make the scope clearer. We will also start annotating which tagging recommendations constitute something new or different from standards found elsewhere. A big issue that’s been raised is with mapping sidewalks as separate ways. One of the biggest benefits to this approach is that it is a step closer to the OSM principle of mapping conditions “on the ground”. It allows an accurate, elegant tagging scheme for the ground conditions of sidewalks, whereas current conventions lead to an explosion of tags for even basic information. Also, by enabling the user to simply add in the location of intersections and kerb ramps where they see them, it makes it much more intuitive for the user, particularly new users, to add data correctly. We hope that making this more intuitive will lead to more contributions and better coverage of sidewalk data. It also resolves several visualization concerns (the wiki has been updated to explain what we mean by this). Finally, treating pedestrian routes as separate ways is more in line with routing concepts (constituting graph edges). For examples of how complex tagging would need to be to adequately describe pedestrian ways using only street lines (and how that graph would need to be derived anyways, likely with gaps in information), there is another proposal ( http://wiki.openstreetmap.org/wiki/Proposed_features/sidepath_tagging_scheme, linked on our proposal), as well as the work of Nathanael Lang that was previously mentioned (https://github.com/Nathanael-L/pedro). At first it seems like the street turn lanes problem, but it has the added complexity of (1) needing to add several annotations to each lane, (2) the lines may intersect in non-trivial ways, and (3) there are almost always features located on or between the lanes (kerbs, ramps, crossings, trees, bollards, grass, bus stops, trash cans, bicycle paths…). There are valid concerns that this proposal could affect routing solutions for those who don't have mobility limitations, and in a related theme, that mapping sidewalks as separate ways may only be appropriate for specific geographies and doesn’t scale so well to the rest of the world. The common challenge can be described as: what happens if I’m in a situation where I’m able to cross the road wherever if I want to? It would be a pain, and clearly inefficient if I was routed to the nearest crossing when I was able to just cross the road. Adding to that, there have been some concerns that the proposal does not take European use cases into account - for example, that it would break routing for users who want to cross the street at any location, or that mapping sidewalk geometries would be inappropriate for certain geographies. We would first like to point out that these use cases also apply in North America, including the U.S., where jaywalking is allowed in many places (regulations operate at the national, state, and local levels). This Mapillary photo in Seattle, WA, US is typical of many residential areas, and has a nearly identical appearance to the example of Cambridge listed in the talk page of the proposal: https://www.mapillary.com/app/ ?lat=47.6924923&lng=-122.3472098&z=17&focus=photo&pKey=50wq0 onWI0tm97JK7Z5s5g. Such a user would naturally cross pretty much anywhere there, and it’s an absolute necessity to walk in the street in areas that don’t have sidewalks at all (some suburbs, e.g.). As a result, we think these are universal concerns and would like to account for them. In cases where the distance to the suggested crossing is short and it is visible where the route continues after the crossing, the user could just choose to exercise their judgement, ignore the router to cross the road (hopefully avoiding cars) and pick the route back up once you’ve crossed. For cases where the distance is significant to the nearest crosswalk there are at least two further options. You could go ahead and directly add a way connecting the sidewalk to the street (as things are currently mapped, in fact), or with a bit of wrangling, you could structure the router (or pre-process the data) to make cross-street connections without needing to ‘invisible’ ways to the OSM data layer. We think it helps to have visuals for these examples, so we’ll be adding them our wiki shortly, please stick with us! It would also be really helpful for us if we could have specific examples of cases where there is a pedestrian routing solution that currently works for the user that would break with our proposed solution :). To the best of our knowledge, all of the large-scale routers rapidly fall back to the street network (ignoring the sidewalk tag) due to the incompleteness of annotated sidewalks. Integrating separately-mapped sidewalk ways with street centerlines (for cycle routing, etc) and areas (plazas) are open problems that aren’t actually specific to mapping sidewalks. There are already numerous pedestrian ways that need to accomplish both tasks, and they seem to work with automatic routers. For integrating with streets in particular, this proposal suggests linking at street crossings and lowered kerb locations, which happens at regular intervals in cities (and is addressed in the last paragraph). Associating sidewalks with a street is a particularly interesting point. This problem is not very different from how buildings associate with streets using either addr:street=* tags or an associatedStreet relation, and we don’t yet have a perfect solution in place (it’s been listed as TBD in the wiki for a while now). Knowing the associated street is not actually necessary to make pedestrian routing on sidewalks work much better than it currently does, particularly for people with limited mobility (and blind users http://stateofthemap.us/2016/osm-lights-up-the-world-for-bli nd-users-with-sound/), though it could probably be enhanced with a tag or street relation (see the Talk page of the proposal for some good discussions on this issue). We’ve tried to address as many concerns as we can, and look forward to more discussions! Thank you, Tom, Meg, Jess, Anat, Nick and Kaicheng. 2016-08-04 1:06 GMT-07:00 Marc Gemis <marc.ge...@gmail.com>: > On Thu, Aug 4, 2016 at 3:35 AM, Mike Thompson <miketh...@gmail.com> wrote: > > I tested out the proposed mapping/tagging scheme in my local area > > (http://www.openstreetmap.org/#map=17/40.49192/-105.05655 - not > claiming I > > did it perfectly). I didn't think it was especially difficult. Drawing > the > > additional ways took a little more time, but offered the advantage that > you > > received a good visual as to whether all the sidewalks had been correctly > > mapped. > >> > >> > > > > Did you miss the crossing of the Stanton Creek Drive near the > roundabout ? Proves the argument that it is very likely that one will > crossings :-) > And without those extra ways, a router will probably allow you to > cross Tortola way while walking allow Basseterre Place on the south > side. Now it, will have to route you south to the roundabout. > > regards > > m > > _______________________________________________ > Tagging mailing list > Tagging@openstreetmap.org > https://lists.openstreetmap.org/listinfo/tagging >
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