taco909 wrote:North side (southbound) 88.6 + 90.4
South side (northbound) 93.9 + 85.8

So we are within 1 degree of 180 on both and we're (barely) within 5% of 90 degrees on the northbound first turn, well within 5% on the rest.... but I've seen a number that were outside of 5% of 90 (by a lot) but still about 180 total and did not route a u-turn.

Does this type a U-turn consistently in live map and app? Or only during severe traffic?

Sent using Tapatalk for Android 4.4.2

taco909 wrote:

PesachZ wrote:

taco909 wrote:North side (southbound) 88.6 + 90.4
South side (northbound) 93.9 + 85.8

So we are within 1 degree of 180 on both and we're (barely) within 5% of 90 degrees on the northbound first turn, well within 5% on the rest.... but I've seen a number that were outside of 5% of 90 (by a lot) but still about 180 total and did not route a u-turn.

Does this type a U-turn consistently in live map and app? Or only during severe traffic?

That needs to go back to KuniaKid.
Everything looks good to me and I suspect it is an issue with traffic (or the legal route) overriding the penalty.

This "penalty" needs to be changed to "restriction"

Try to test it in livemap, can you get livemap to route the U-turn? I can't check now, so I ask.

Sent using Tapatalk for Android 4.4.2

taco909 wrote:

PesachZ wrote:

taco909 wrote: That needs to go back to KuniaKid.
Everything looks good to me and I suspect it is an issue with traffic (or the legal route) overriding the penalty.

This "penalty" needs to be changed to "restriction"

Try to test it in livemap, can you get livemap to route the U-turn? I can't check now, so I ask.

I can't get a pair of segments that will route a U-turn cleanly on the south side.

I do get one routed on the north side, but the trace from Livemap does not overlay the segment in WME... the angle of the approachy is significantly different.
It shows KuniaKid edited the segment yesterday, I suspect an adjustment was made either after posting (and before I checked the angles yesterday) or before posting and KK was looking for confirmation.

I'm thinking it WAS outside of the allowed angles to enable to penalty, but should be OK now.

Would be nice if KK would confirm so we aren't spinning our wheels for the next 2 pages.

kkturn.jpg

I agree with your analysis. I believe the penalty is very strong, and have only seen the penalty fail because of traffic at one intersection. I agree it's much more likely that it didn't meet the wiki listed criteria, and now it will be fine.

Sent using Tapatalk for Android 4.4.2

spookyx wrote:From my tests and experience, if a segment is 15 meters it will not alway do a U turn.
If, however is 16, than you will get a U turn on 100% of cases.

You must take into account rounding in WME. Which is why I always recommend using <14 or >16. Do you have examples?

Sent using Tapatalk for Android 4.4.2

codgerd wrote:Another example of u-turn route allowed when it appears the rules are being followed correctly to prevent it. Median has no geometry and is 13.8 m, total angle of incoming / outgoing segments is 183 deg.

Permalink




Cheers

The roads were edited today to make the median smaller, but that wasnt necessary. If you test it in livemap you'll see you can't reproduce that route. From the UR trace it does seem like it was a recalcuation on that last segment before the uturn, which is a known cause of prevention failure.

codgerd wrote:

PesachZ wrote:The roads were edited today to make the median smaller, but that wasnt necessary. If you test it in livemap you'll see you can't reproduce that route. From the UR trace it does seem like it was a recalcuation on that last segment before the uturn, which is a known cause of prevention failure.

With enough persistence I am able to reproduce a u-turn at that intersection in livemap:



I had to try several variations on a theme, but eventually I was given the u-turn as a suggested route. The editor who responded to the UR has indicated that this intersection has historically suggested sporadic and infrequent u-turns.

I notice that the route saved by the UR u-turned on Boul Laurier then headed south on Aut 73. The wazer instead headed north on Aut 73. Was this what made you think a recalculation was involved? I'm not sure I follow.

At any rate, I do seem to be able to invoke a u-turn in livemap. Where does that leave us?

first lets make sure it is reproducible when not at the beginning of a route. To do this you would have to move your start point further back so it is at least several full segments before the U-turn. Then if you can still reproduce it, we will have to wait for a tile update and test again (since the segments were just edited today. If the U0turn still works after that we can try to have staff investigate it, for that we wil need the livemap PL for the route with the uturn in it.

codgerd wrote:

PesachZ wrote: first lets make sure it is reproducible when not at the beginning of a route. To do this you would have to move your start point further back so it is at least several full segments before the U-turn. Then if you can still reproduce it, we will have to wait for a tile update and test again (since the segments were just edited today. If the U0turn still works after that we can try to have staff investigate it, for that we wil need the livemap PL for the route with the uturn in it.

TheLastTaterTot's proposed new page on the mechanism does warn that u-turn prevention can fail when the u-turn is the first segment of a route or re-route. That may have been what happened to the UR, granted, it's hard to tell. However, my livemap route also offers the u-turn, and it starts on the 4th full segment prior to the incoming segment of the u-turn. Is this sufficient distance? When you say "at least several full segments before the u-turn" it appears to contradict the new wiki guidance, which says the mechanism can fail when it's the first segment of a route/re-route. Shouldn't one full segment prior to the incoming segment be enough? In my case it's 4 segments prior to that, and it's still failing. I know you're fully involved in the thread discussing the new page - are there additional undocumented conditions that can cause u-turn prevention to fail?

Thanks for the help/insight - it's much appreciated.

the "one full segment" we know for sure, but we dont know for sure if 2,3,4, or 5 segments, or a specific linear distance has the same effect. If more than 5 full segments still allows the uturn, send the PL and I'll try to ask staff to investigate.

codgerd wrote:

kentsmith9 wrote: I believe we do include all that we know and to your point I think we have just not thought about adding that particular point into this page. I see no reason why we should not include it once we have enough to confirm how it affects this operation.

Fair comment... I should do well to remember that the wiki is always a moving target. At any rate, if PesachZ says it's definitely more than 1, and possibly up to 5 segments, that'd be definitely worthy of inclusion. Thanks!

correction, I can only commit to definitely one segment. More than one or any other number, or linear length is mere speculation with no evidence to back it up. You sample here may prove to become the needed evidence to further elaborate that warning. But it would be prudent to first investigate properly, rule out other sources of failure, and try to debug it. Once that is complete we should definitely add it to the wiki.
The wiki generally contains knowledge known to be true, it not a good place for speculation, thats what we do here in the forum. Once a thing is settled, it is added to the wiki and codified.

taco909 wrote:

codgerd wrote:As a test, the central median was shortened to 9 m, and the angles were adjusted to exactly 90 degrees, as per the voodoo sometimes recommended on the forums - and contrary to official guidance which says that 14 m and 175 to 185 degrees total angle of incoming to outgoing segment should be sufficient to prevent u-turns.

We've found that 175-185 is too wide of a range and WILL route.
The official guidance of 180 +/-5 is a bit foggy and it seems that it's more a total span of 5 degrees around 180 (180 +/-2.5). It's definitely not 180 +/-5% (+/-9 degrees) that was originally indicated.

I have not encountered any issues in the 178-182 range, but I personally do my best to get the sum to between 178.5 and 181.5 (same as I'll shoot for 174 on permitted u-turns on bowties)
Likewise, we've not encountered issues at skewed intersections where the angles might be 60/120 rather than 90/90, though it is absolutely acceptable to dogleg to 90, and it helps prevent confusion on angles that could lead to a "stay/exit" rather than a "turn"... or worst case (we had this) where segment type and name changes result in the "stay right" capturing Best Continuation, which ends up with all kinds of oddball instructions.

If I've got an oddball that is difficult to get the permissives outside of 175-185 while keeping the restricted legs at 180, rather than mess with the angles I'll just make it a clean 16m box and add AGCs for the prohibited legs, same as if the median is too wide to cleanly use a 14m box.

I wrote the official guidance, and in no iteration that I can think of was the threshold ever suggested to be ±5%, it was ±5° as soon as it was introduced.

codgerd wrote:

taco909 wrote:We've found that 175-185 is too wide of a range and WILL route.
The official guidance of 180 +/-5 is a bit foggy and it seems that it's more a total span of 5 degrees around 180 (180 +/-2.5). It's definitely not 180 +/-5% (+/-9 degrees) that was originally indicated.

The (pre-edit) u-turn permissive setup had a total angle of 183 degrees, within the official guidelines but outside of what you're saying here. So it would be your guess that it was bringing the total angle to < ~182.5 degrees that did the trick, rather than bringing the centre segment from 14 m to 9 m? If so, maybe I will lengthen that centre median back to 14 m, while keeping the total angle steady at 180, and see whether that continues to do the trick.

If what you're saying here has been shown to be true generally, why does the new proposed page on controlling u-turn penalties use the deprecated +/- 5 degrees from parallel? Wouldn't it make sense to incorporate your data (i.e. +/- 2.5 degrees from parallel) into the official guidance?

Cheers
codgerd

This data (±2.5°) was not incorporated into the guidance for two reasons;
A) it was never mentioned in the forum thread for updating that content, and
B) it was never tested and reproducible with public peer review that I or the other authors were aware of.

codgerd wrote:

DwarfLord wrote: It's possible that either a 9-m (or less) cross section or a total inside angle < 182.5° will do the trick. If you don't mind a tiny bit more testing, it would be great to to know if a 9-m segment with the 183° total angle also prohibits the U.

Good suggestion. I'll try both scenarios: 9 m segment with 183 total angle, and 14 m segment with 180 total angle and report back.

Alternately, couldn't we just find out which bar the Waze routing developers hang out in and buy them a few rounds to get them talking? [emoji38]

The information you see now in the page, and its new overhaul is directly obtained from the waze Devs. We got them talking, they told us about the ±5°. They also told us that the angles are measured based on the two segments relative to each other, and not the median, allowing the penalty in skewed intersections. This information is believed to be the most current available, and was tested by several editors, myself included, and found to accurate.
This is also believed to be the intended operation, if other behaviour is found, it is assumed to be a bug we should report to staff. Rather than try to edit around the assumed bug by making AGCs, or changing guidance to be ±2.5°, we should show staff the examples and allow them to fix it.

That all said, if this is truly the behavior, and an adjustment from total angle of 183 to 182° does fix a problem we need samples to show staff and get it fixed. So please let us know if you find anything. Things can always change around here by accident or on purpose.

Sent from Android using Tapatalk

What you're sounds like prudent best practice editing, and I wouldn't discourage it as a practice. As far ±5°, I went back and forth a few times to confirm that's what they meant.

Sent from Android using Tapatalk

Edit the exact quote was …180° (give or take 5°)…