Changeset: 61631661
remove sidewalk not connected to street network to avoid routing problems
Closed by TheBestIdea
Tags
changesets_count | 1229 |
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created_by | iD 2.10.0 |
host | https://www.openstreetmap.org/edit |
imagery_used | Bing aerial imagery |
locale | en-US |
Discussion
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Comment from jmapb
There are dozens of these around Brooklyn and Queens, all added by homeslice60148 and tagged with #maproulette and #Long_Island_traffic_lights_(Brooklyn,_Queens)
Aside from the facts that 1) they're generally not in places where sidewalk mapping makes any difference to pedestrian routing, and 2) they're left unconnected on the ends, so they're actively problematic for routing... they seem really well done. So I've left them alone, figuring it's a work in progress, and I've never tried to contact the mapper.
Do you think these should all be purged?
I have no experience with maproulette, but is this something that can be fixed or prevented from that end?
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Comment from TheBestIdea
My personal preference is that, in NYC where sidewalks are the norm, if they just follow the geometry of the road, they should be mapped as an attribute of the road with the "sidewalk=" key and not as a separate way.
When they're disconnected at the ends so that they actively impede routing, I usually remove them. I don't know anything about maproulette either. -
Comment from bhousel
It would be great if, rather than removing the sidewalks, you would just connect them to the road where crossings exist. It's not a matter of "personal preference" - there are groups working on wheelchair routing that need to map attributes on the sidewalk ways (like smoothness and obstacles) which would be too cumbersome to add as attributes on the vehicular road. Thanks!
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Comment from TheBestIdea
There appears to be a robust debate about whether sidewalks should be separate ways: https://wiki.openstreetmap.org/wiki/Sidewalks#Sidewalk_as_separate_way If people want to take to time to do so, I'm not going to stop them, but they should do it in a way that does not impede routing for other users. It is also legal for pedestrians to cross the street mid-block in many places in NYC (any block there is not stoplight at both ends) and "just connect them to the road where crossings exist" fails to account for that.
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Comment from bhousel
Yes, I'm aware of the wiki page. Again, the primary usecase for this style of mapping is for wheelchair users who can not cross the street mid-block. It does not impede routing for other users (I'm not sure why some people think this).
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Comment from jmapb
None of these #maproulette #Long_Island_traffic_lights_(Brooklyn,_Queens) sidewalks have any wheelchair or smoothness info. I've actually never seen any such info on sidewalks here. (I have seen sloped_curb=yes on some *road* intersections, but that's obsolete now.) Yes, it might be added someday, but it might be added someday via sidewalk:* tags on the road as well -- that's the very first example given in the Sidewalks wiki page. Doesn't seem "too cumbersome." Regardless, the state these are being left in is an active impediment to both pedestrian and wheelchair routing. It can't really be justified by saying "maybe someday someone will want to add wheelchair tags."
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Comment from jmapb
Personally I only map sidewalks when I perceive that it would improve routing, but I can easily imagine that at some point in the future mapping every sidewalk will be the norm. I'm not inclined to fight against this -- but I do want people to map responsibly, so that the map isn't less useful after their contributions than it was before. Maybe https://wiki.openstreetmap.org/wiki/Sidewalks#Sidewalk_as_separate_way needs some good idea/bad idea examples for how to tie mapped sidewalks into the existing street grid.
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Comment from jmapb
BTW here is a very silly example of screwed up pedestrian routing. (Wheelchair routing would have the same problem, I believe.)
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Comment from bhousel
jmapb, please leave me alone. If you need help adding a crosswalk to fix that routing issue, ask on help.openstreetmap.org
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Comment from jmapb
These comments are not a personal attack and your defensiveness is uncalled for. I'm discussing the changeset. If you don't want to part of the changeset discussion, hit the "unsubscribe" button.
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Comment from MikeN
I've observed new mappers drawing these types of sidewalks without crossings because they appear to 'stop at the curb'. They're just entering an observation. I'd see it as a work in progress, and not usable for navigation on its own until the network has been fully entered..
A community might decide to map sidewalks integrated with streets or separate ways, but if they're watching closely, they can advise new mappers of the preferred method. -
Comment from jmapb
I don't think these are being mapped this way because they stop at the curb -- there are clearly visible crosswalks at all of the hanging ends. I don't know whether homeslice60148 prefers to map this way or if it's part of the maproulette instructions (? I don't know how maproulette works. You, Mike, seem to have some experience though!) I messaged homeslice60148 regarding this changeset discussion, so maybe we'll see.
I don't think we're going to be able to come to any agreement on the sidewalks-as-ways issue anytime soon, but I do like the idea of basic guidelines for how the sidewalk ways should be tied into the street grid when they *are* mapped, to avoid routing problems. -
Comment from jmapb
BTW this changset (61631661) has been reverted by changeset 61662763 (restoring the deleted sidewalks), and the loose sidewalk ends have been tied into the street grid by changeset 61662897. This will improve the routing. It will still be a left and two rights to get from 691 Fulton to 239 Ashland Place, for instance, but I think we can all agree that it's an improvement over this:
https://imgur.com/50v4S2R
What I'd suggest as a standard would be this:
https://imgur.com/PZGVrHO
Routing would still have some little wiggles of course, no way to prevent that, but there'd be no real wrong turns or backtracking. (And I'll go ahead and upload this in a bit.) -
Comment from TheBestIdea
I agree that your suggestion would be a big improvement.
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Comment from jmapb
Happy to hear it. And MikeN. by the way, I believe I misread what you meant by "end at the curb" -- yes indeed, the sidewalks themselves do literally end at the curb, crosswalks or no, and I can easily imagine a mapper choosing to map them in this literal fashion without realizing that it affects the routing.
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Comment from jmapb
Well I added my sample "cap" at the Fulton/Ashland place, changeset 61672263. If there's ever a consensus to purge these loose-end sidewalks that survives the edit wars, please feel free to get rid of that too -- it's only useful IMO as a fix to routing problem the loose ends cause.
Homeslice60148 has not responded to my invitation to join this discussion... Other than following homeslice around and patching the loose ends (which I'm not inclined to do) I don't think there's anything to be done about it, and the pedestrian routing will be damaged for the foreseeable.
(If I have too much coffee someday I might bring this up on one of the mailing list, with the aim of improving the Sidewalk_as_separate_way section of the wiki.)
J
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Comment from homeslice60148
Hi everyone!
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Comment from homeslice60148
Whoops, let's try this again. Hi, everyone! I just noticed jmapb's message and I'm jumping into the discussion here to let everyone know what I'm doing and why. I am a very long time mapper on OSM, and it is my general goal to improve the map. I personally follow the "do no harm, delete no correct data" mantra in my mapping.
1. The Maproulette project instructions DO NOT say to add sidewalks. I am doing this as a sort of sister-project that coincides with the official "check intersection" project. My rationale is that, if every intersection in Brooklyn is done, then the crossings may as well be done at every intersection, and then if the crossings are done, than the sidewalks may as well be done, too.
2. I map sidewalks from the intersection of assignment on Maproulette until the next street to street intersection (residential or higher). This way, my methodology of pairing the two tasks stays in tact.
3. Following the logic of OSM standards for separating dual carriageways, sidewalks should be mapped as separate ways. As there is a physical boundary between the road and the sidewalk, they should be mapped separately. This allows individual tagging, for example surfaces. The road may be cobblestone while the sidewalk may be concrete. Cars and (for the most part) bicycles are not allowed on the sidewalk, and pedestrians are not allowed on the road. The land-truth physical separation of sidewalks and roads should be represented on a map where something as small as a fire hydrant can be accurately mapped.
Yes, the routing will be screwed up for a while, but I am mapping each of these individually, and I can't do all of Brooklyn in one sitting!
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Comment from jmapb
Hi homeslice, thanks for joining us -- I shouldn't have given up so quickly! And thanks for being clear about your goals and MO.
As I said, I've admired your sidewalks. But I hope I've also demonstrated the downside this mapping technique has on the pedestrian routing.
When sidewalks are fully mapped, of course, the pedestrian routing improves, and, as bhousel mentioned, it creates opportunities for detailed mapping of the sidewalk ways that may assist wheelchair users, etc. In the mean time, though, these islands with loose ends will break pedestrian and wheelchair routing for years to come. There are over 4000 intersections in Brooklyn, and a ballpark estimate is that it would be 6 or 7 years before you're done. Of course, the process may speed up as others chip in! But we're looking at years of broken routing nonetheless.
I'd ask you consider connecting the loose ends to the road network so the presence of the sidewalks does not negatively affect the routing.
Offhand I feel that capping the loose ends with the four-crosswalk way like I added at Fulton & Ashland is the best way to transition between a sidewalk-mapped block and its sidewalkless neighbors. And if it is in fact your goal to completely map the Brooklyn sidewalks, then it's something you'll want to do eventually anyway,
I'd love to hear other suggestions if you or anyone else has them, though, since I do a fair amount of this myself (connecting paths and sidewalks to the grid) and I want do what's in the best interest of the map.
Thanks again for joining us, J -
Comment from homeslice60148
J,
I think the solution of closing the crosswalks for routing will work. I will do this from now on. -
Comment from jmapb
Thanks! (Btw I think I mapped your place today: https://www.openstreetmap.org/node/1829661485 )
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