Summary: In Potlatch 2, how to create a no-u-turn restriction with a "via" member that is a way (as opposed to a node)? This is necessary when the intersecting roads are divided and an intersection is represented by four nodes rather than one.

UPDATE

I have deleted most of my original post. I realize that my problem was not with the schema for turn restrictions, but with the way it is implemented in Potlatch 2. Due to the way Potlatch 2 "simple" mode allows one to easily create no-u-turn restrictions with a via node, it did not even occur to me that via could be a way.

So really my question now becomes: is there a "simple" way to create a no-u-turn restriction in Potlatch 2 where via member is a way?

Here is what I do now:
1. Split ways inside the intersection as needed.
2. Ctrl-click (Command-click on Mac) one side of the road, the short section of the cross road to the left of it and the reverse side of the road.
3. Add all three to a new relationship.
4. Set relationship to Advanced->Turn restriction.
5. Set type to No U turns.
6. Click Members and set roles: to, via and from (have to type).

Can this be simplified at all? Is this a wishlist for Potlatch?

asked 04 Mar '11, 20:06

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ponzu
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edited 16 Mar '11, 05:18


> is there a "simple" way to create a no-u-turn restriction in Potlatch 2 where via member is a way?

Not as yet, no. The dedicated turn restriction editor currently only works where the via member is a node.

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answered 05 Mar '11, 12:19

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Richard ♦
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accept rate: 19%

Thanks. Is there a Potlatch wishlist?

(05 Mar '11, 14:58) ponzu
1

I'm getting the feeling you're mapping in greater detail than Potlatch was intended. You can use Potlatch to map a large area with rich detail, but it makes about as much sense as driving to Chicago from Tulsa on a bicycle. Likewise, you can use JOSM for a quick, single edit, but it makes about as much sense as driving a car to the corner store...

(05 Mar '11, 18:46) Paul Johnson

Interesting analogy. I have a feeling I have to get into JOSM, but I just wanted to point out that if Potlatch authors went to the trouble of implementing the wizard for creating no_U_turns with a "via" node, they might as well create one for when the "via" is a way. It could actually be even easier (to use) than the existing UI. Click three ways in order, click Transport->No U Turn. It could save a lot of clicks to the users.

(05 Mar '11, 21:34) ponzu

Plus it was Richard who said "not yet" thus implying that it may be coming. I just wanted to know if needs my vote.

(05 Mar '11, 21:35) ponzu
2

ponzu - it will be coming, yes; you can add a trac ticket to request it as an enhancement if you like (that'll remind us to do it :) ).

Paul - disagree absolutely. There is nothing intrinsic to Potlatch that makes it unsuitable for large edits; similarly, there's nothing intrinsic to JOSM that makes it unsuitable for drive-by edits. I've done, and continue to do, lots of large edits in Potlatch. It's simply a matter of personal preference.

(06 Mar '11, 12:03) Richard ♦

Except for the whole "potlatch is unbelievably slow with large datasets" and "potlatch tends to lose it's lunch before saving on large datasets"...

(06 Mar '11, 19:14) Paul Johnson
showing 5 of 6 show 1 more comments

I have used a way as the "via" member in the relation successfully using mkgmap, so at least one renderer understands a three-way, no node U-turn. As far as splitting ways, only ways that are separated by a median (open or closed) should be seperated into two ways on the map (note that two-way left turn lanes and a single set of centerlines is not a median for purposes of mapping). For u-turns on a single way, using the same member entered into the relation twice for both the from and the to members, with a via node should work.

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answered 04 Mar '11, 21:47

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Paul Johnson
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accept rate: 10%

edited 04 Mar '11, 21:48

I understand and I only split ways that are physically split with a median. Also, I am not doing it for my health, but to eliminate massive problems with phantom left turns across the divider. I also have no problem mapping "no u-turns" on a single way and would be extremely surprised and disappointed if a routing algorithm misinterpreted those. For your first point, I need to understand better what you mean. Can you share a link to wiki and/or map that has those?

(04 Mar '11, 22:10) ponzu

Paul, is it your opinion that it is impossible to properly map a u-turn restriction using any of the configurations described in my question (for the reasons stated)?

(04 Mar '11, 22:13) ponzu

Honestly, I didn't understand your description, so I answered as best I could with the information I did understand; if you have mapped any in the way you describe, relation ID numbers would be great. And you're right to split divided roadways with a median into two different ways. Two relations in the vicinity of Shadow Mountain in Tulsa are demonstrations of restrictions involving a way for a "via" member: http://ra.osmsurround.org/analyze.jsp?relationId=1341305 and http://ra.osmsurround.org/analyze.jsp?relationId=1341304

(04 Mar '11, 22:28) Paul Johnson

Memorial Drive and 61st, immediately east of both relations and running for several miles both north and south is a good example on how to map a divided roadway. Memorial Drive has driveway stubs added, and this touch really helps when trying to navigate along it with a GPS device.

(04 Mar '11, 22:31) Paul Johnson

Thanks, I did not know I could use a way as the "via" member. I restated my original question.

(05 Mar '11, 09:37) ponzu

A lot of tools seem to disagree with me on this (the turn restriction plugin in JOSM, for example, complains loudly about editing one of these), but in practice, it seems to work.

(05 Mar '11, 16:03) Paul Johnson
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question asked: 04 Mar '11, 20:06

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last updated: 29 Nov '17, 11:51

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