How should the the turn restrictions for this junction be represented in the OSM data?

Complex junction in Salford

Also, some follow up questions:

  • In iD I can only figure out how to add simple turn restrictions - from way, via node, to way - not the more complicated turn restrictions with ways as via elements. Is this expected?
  • I think I could represent the turn restrictions using such simple turn restrictions, if I added a diagonal way from B to D. But that would mean duplicating roads for routing purposes. Would this be frowned upon? What about splitting a way into two ways for the same purposes?
  • If turn restrictions via ways are needed, are there any routing engines that support such restrictions so I can check my edits behave as I expect, to check my work for errors? I understand OSRM doesn't ?


asked 15 Aug '15, 21:50

michaelt's gravatar image

accept rate: 0%

alt textThe tagging of the routing through any junction requires that " one ways" and junction "nodes" each have the correct restrictions. Once you have done all of them you will have to wait for the routing engines to use that data. This is my question when i struggled with a pair of simpler junctions you could also use an editor to inspect similar junctions, to learn by example. We now have some excellent routers accessible from the map page that can now be used to check routing .. but you may have to wait for recent edits to be used by the routing engines.

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answered 16 Aug '15, 11:26

andy%20mackey's gravatar image

andy mackey
accept rate: 4%

edited 19 Aug '15, 06:53

Looking at the present tagging of your junction it may not need any additional turn restrictions as the one ways seem to do the job. The jpeg shows the results that one router gives. Does this agree with the road signs?alt text

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answered 18 Aug '15, 21:00

andy%20mackey's gravatar image

andy mackey
accept rate: 4%


Both OSRM and MapQuest allow traffic from A to D, from C to B, and U-turns from A to A and C to C. None of these are allowed according to the road signs..

(18 Aug '15, 23:08) michaelt

I think i understand now. I'll see if i can get to grips with iD's functions

(19 Aug '15, 06:23) andy mackey

Initial tries suggest some new turn lanes may be needed, and turn restrictions at each individual node where necessary.

(19 Aug '15, 06:27) andy mackey

I did not add any turn lanes. I found that iD as very good turn restriction editing facilities. I have mapped some or all of them, You can inspect or change them of course. We can now wait and see if they work correctly when the routers get to use the updated info.

(19 Aug '15, 06:50) andy mackey

I have added some turn restrictions to your junction with iD. The tool to do this is neatly implemented in the iD editor. We will have to wait and see if they work, but I suspect that you are correct in your question that some restrictions might not be easy to map.

(19 Aug '15, 07:15) andy mackey

I was so impressed with iD's turn restriction implementation that I thought i would share them. It works like this. Start iD. Click on the junction node, click on the "in Way" and then "out ways" show red or green indicator, to change a red or a green one just click on it to toggle or swap over, Excellent. well done iD Guys.alt text

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answered 20 Aug '15, 08:26

andy%20mackey's gravatar image

andy mackey
accept rate: 4%

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question asked: 15 Aug '15, 21:50

question was seen: 2,767 times

last updated: 20 Aug '15, 08:26

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