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Suppose you have this actually fairly common scenario: you have two one-way streets crossing each other. One is northbound, other is westbound. There is an "explicit" no right turn sign on the northbound street prohibiting an eastbound turn...which would be against the flow of traffic, which is the "implicit" turn restriction.

Now I've been noticing people adding in the explicit turn restriction in and just leaving the relation unfinished because it's impossible to add the other elements with iD and possibly other editors due to the one way.

Should these turn restrictions be fleshed out somehow (perhaps add a sign saying so) or flushed out (remove the turn restriction in its entirety)? These unfinished turn restrictions both cause a KeepRight issue as well as cause a warning in mkgmap, so I've been deleting them due to the implicit nature of the restriction -- but should they still be marked, and how?

asked 10 Jul '19, 17:12

gpserror's gravatar image

accept rate: 0%

I've never seen an unfinished turn restriction. Do you have an example?

(10 Jul '19, 17:19) TZorn

Take a look at relation/restriction 8111223 (if I haven't fixed/deleted this restriction yet) - my guess is that there's a sign there and the original mapper tried to put the spirit of the sign in, but could get the rest of the relation in.)

Some others to look at: 6915842 9129946 7157302 -- again caveat that I haven't fixed them. Since there are thousands of these in the USA alone, this would take effort to fix them.

(10 Jul '19, 17:52) gpserror

The history of those relations shows that each one was a complete turn restriction relation initially, but that ways have since been removed from the relation. This looks simply like contributors introducing errors while editing existing data, not faulty mapping from the start or an editor issue.

(10 Jul '19, 18:54) alester

Ah interesting. In any case they still need to be fixed but unsure what's the best way to proceed. Seems like some editors have better protections against breakage.

(10 Jul '19, 19:21) gpserror

Here's a restriction ID with no history (no u-turn): 8385537 But yes, it looks like a lot of restrictions are broken due to moving roads around.

Sigh... some of these restriction relations are harder to fix than I thought. Back to the drawing board...

(13 Jul '19, 18:29) gpserror

Something has gone terribly wrong there. A valid turn restriction at that intersection exists with 8385544. Have a look at the corresponding changeset. There are more broken and valid relations in there.

(13 Jul '19, 22:36) TZorn
showing 5 of 6 show 1 more comments

If a turn restriction relation is broken and at the same time unnecessary I would delete it. But I would leave a changeset comment to the original mapper explaining the issue.

If the turn restriction is working and valid, just unnecessary I would leave it as is. We should try to avoid destroying other mappers' works even if we would do it differently ourselves.

permanent link

answered 10 Jul '19, 17:22

TZorn's gravatar image

accept rate: 15%

Thanks, that seems to be what I've been doing and leaving an explicit detail in the changelog why I removed them - I was a bit concerned as, well, there IS a sign there and the original mapper was trying to reflect the spirit of the sign. I haven't removed redundant restrictions ("working and valid"), in fact I would not even know that they exist as I'm only touching restrictions causing mkgmap/KeepRight warnings :)

I guess the last case is if it's unknown if necessary (can't verify) and also broken. KeepRight flags these but there haven't been changes for many months. I see this a lot. I try to look at Mapillary to see if these are needed and try to correct it but sometimes there's just not enough information.

I suppose a red X (map note) is needed for these? I'm just afraid I'm duplicating flagging as KeepRight marks them as light blue already -- though not everyone looks at KeepRight.

(10 Jul '19, 17:46) gpserror

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question asked: 10 Jul '19, 17:12

question was seen: 1,234 times

last updated: 13 Jul '19, 22:37

NOTICE: is no longer in use from 1st March 2024. Please use the OpenStreetMap Community Forum