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[NEW] Best Continuation algorithm has been changed

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It has recently come to our attention that in the past week or two Waze has altered the algorithm used to determine the Best Continuation at a fork in the road. This was first posted about in the wiki update thread, but I'll leave that thread for discussing the upcoming necessary changes to the wiki to reflect this change. I'm creating this thread to alert other editors to this fact, which is already causing lots of URs.

In short: the algorithm looked for a match from the segment preceding the junction, to either of the segments after the junction. It first checked for a matching primary name, if it didn't find any it then checked for matching segment types. If a match was found that was the Best Continuation, otherwise both segments would get an instruction.

The good news:
The Best Continuation is only a factor when 2 or more segments leave a junction at less than 45° turn angles. (e.g. a fork in the road, an exit from a highway, a Wayfinder, etc.) This has no effect on turns which would give a "turn right/left" instruction, only ones which would give a "keep/stay/exit right/left" instruction. For a clearer understanding of the whole Best Continuation topic, please read the wiki page linked above.

The other news:
Alternate names now play a role in factoring which segment will be the Best Continuation! This is a very recent development, and can cause many highway exits, wayfinders, and road splits which were previously giving the proper instructions to have suddenly either stopped giving an instruction to a segment which needs one, started giving an instruction to a segment which is the clear continuation and doesn't need one. We still do not fully understand the full extent of this change, and how different variables are being taken into consideration in the algorithm. There is extensive testing underway (which will be documented in the wiki update thread) to determine all these variables.
What we have tested thus far, the following matches will be BC in order of preference:
  • Two primary names AND their road types
  • Two alt names AND their road types
  • Two primary names only
  • Two alt names only
  • When there is any alt name on the preceding segment, there can be a cross-match between an alt name and a primary name (the alt of one segment matches the primary of the other)
    • If one side is a primary match, and the other is an alt match and a road type match, the side with alt and type match is BC (This is the first time we have seen a primary name match not be the BC)
    • When there is no alt name on both segments in a pair, alt names are not considered for matching
    • City names do not seem to affect this at all
    • There is no preference given to the order of the alt names
EDITED list for clarity

What do you need to know for now.
If you see URs, complaining of this behavior, please investigate them carefully, run the route through Livemap to be sure if the instruction has now changed, even if all the segment names appear correct in WME. Bear in mind that any Continue instruction shown in Livemap with a straight arrow is NOT given in the client. If you find a problem caused by this change, please don't edit anything, and post the PL to this thread so we can investigate it to help us learn the full extent of this change. After reviewing it, we will fix it to make it work properly again.

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Last edited by PesachZ on Tue Sep 16, 2014 9:55 am, edited 2 times in total.

Post by AlanOfTheBerg
I do agree that best continuation algorithm has changed, but I do not think it was purposeful, rather an unintended consequence of fixing a feature of detour prevention. I have not seen any confirmation from Waze HQ that this was intended. Therefore, I believe the posted guidance here may be premature.

If someone has confirmation from Waze that this is now working as designed and segment name in Alt only (not city also) is used for best continuation calculations, then I rescind my concerns.
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Post by AlanOfTheBerg
Based on the last post I read from Waze a few moments ago, it appears they plan to go forward and not back out this change.
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Post by asterix06
Why anyone of Waze Staff didn't asked anything to us , before to make such a type of important changes on the alghoritm ?

Many many users have been faced with strange routing behavior , where we could hardly give an answer and creating a lot of URs as well.
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Post by asterix06
Marc is correct !
Are we sure modifications and algorithms are the same for all platforms ?


Inviato dal mio iPhone utilizzando Tapatalk
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Post by bz2012
I am interested in what the new 'decision chart' will look like, so i can modify mine. :)

It sure would be nice if WAZE would share this stuff with us so we don't have to reverse engineer it ourselves. :!:
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Post by bz2012
Is this a victim of the change?

https://www.waze.com/editor/?zoom=5&lat ... 924&zoom=0#
Problem: there is a split here. need keep right / keep left instruction
Reported on: September 10
I have no idea if it was working before, but hope/assume it was as last change were in late July.

s-in US-59 HOV, Houston, Texas; mH
s-out 1 US-59 HOV, Houston, Texas; mH 164 deg
s-out 2 <no name> ; ramp 187 deg
no alt names involved.

Suggestions for fixing?
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Last edited by bz2012 on Wed Sep 24, 2014 1:05 am, edited 2 times in total.

Post by bz2012
corrected. :) Sorry. My bad!
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Post by dckj
hmm... this 1 doesn't work anymore
the KR segment used to work until yesterday or so when it stopped working. the KL segment is still working...

https://www.waze.com/editor/?env=row&lo ... =104262344
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Post by dckj
@shaq23 @pesachz

guys, thanks for your time yesterday. however, a recent finding by a fellow editor L5 @Krixera has ruled out the elevation theory...

https://www.waze.com/editor/?env=row&lo ... =104405543
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