I agree that mapping things that are “merely proposed or planned” is controversial. I have experienced first-hand (with significant consequences) that doing so is “discouraged,” at least initially before wider understanding of the specific example / project begins to allow heads to nod. Accordingly, I have mapped such things in specific cases and for specific reasons and our community continues to “allow” these, especially as wider understanding of the specifics takes place. I illustrate examples:
In California (USA) the nation’s largest public works project (~$100 billion) is underway: California High Speed Rail is being built. Without getting into the highly controversial and contentious details of this transformative infrastructure, its detractors, funding difficulties and “scaling back” (by our Governor) have presented great challenges to how OSM maps this. I have endeavored to capture statuses as best as OSM’s tagging (
railway=construction…) allows us. Please see California/Railroads/Passenger - OpenStreetMap Wiki and observe how a table of five segments of the project are colored green/yellow/red and rather accurately indicate progress and statuses. Note especially how the future-oriented segments (of Phase 2, colored red) are said to be “barely there” (in OSM) and how ephemeral is their existence in our database.
Here, we find significant segments of even the proposed segments where both planning (about $90 million of public works “design contracts”) as well as sometimes “on the ground” preparation work are “officially underway” (like bulldozing the right-of-way, even though no specific design is complete nor construction contracts exist), even in the “proposed” segments. It isn’t actual “construction,” yet, it is accurately tagged “proposed” because that’s what it is. This type of “this IS going to happen” (but hasn’t yet) is exactly why we have tags like
railway=proposed. While something like this probably has (rarely) happened before, it isn’t likely that $90 million of design contract money will turn in to a project that never materializes. Given all that, and the real value that having these (even “barely there”) proposed (quite major) infrastructure elements in our map represent, the community has seen fit to allow them to remain.
In another example, “numbered national bicycle routes,” as part of United States Bicycle Route System - OpenStreetMap Wiki , a convention has emerged over the last 10 years to use
state=proposed to indicate routes which (it is true) do not (yet) exist, but which are so close to becoming “Approved” (in the System, see our wiki for details on how this happens) that it really makes sense for us to enter them. It will only be a matter of weeks (or a couple months) before they likely DO become Approved, and this gives OSM the time and flexibility to enter these (often hundreds or even thousands of kilometers of) routes into our map while they are “on ballot” (for consideration to become Approved). After they DO become Approved, OSM merely removes the
state=proposed tag, and (bicycle route) renderers re-render the dashed lines into solid lines, presenting the world with a beautiful, growing, accurate network of said routes. While there was quite prickly resistance to this process (as it emerged circa 2012-14), it has become both well-established (in OSM’s implementation of USBRS) and well-accepted among our community that “we enter routes (as proposed) like this.” And hence, it is OK.
The bottom line is that tags like
highway=construction are always OK, if actual on-the-ground construction is taking place, but for the concept of “proposed,” we must be much more careful. “Proposed” (or “planned”) cannot be used for “fanciful musings” or “wishful thinking,” it may only be used when things like funding kick into reality, other “existence proofs” (for the project) begin to exist, AND that there is wide community acceptance / consensus that this IS taking place. Then and only then might a “proposed” tag be considered for OSM. Speaking first-hand, this is not easy to achieve, but it is well-worth the effort to do so, as I am certain that this makes for a map more complete with comprehensive, lifecycle-aware data. But again, it must be used carefully and with wide discussion that it is appropriate. I hope these two examples (CAHSR and USBRS) can be exemplary in how OSM does so.
Thank you for reading.