[Page Update] How Waze determines turn/keep/exit maneuvers

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Re: [Page Update] How Waze determines turn/keep/exit maneuve

Postby pumrum » Sun Oct 12, 2014 10:24 pm

Out of curiosity, was anyone able to confirm that this is not a bug? It seems really counter-intuitive to have a properly configured ramp segment not deliver an "exit right" instruction just because the alternate name is the same.

In CT, almost all streets including numbered and signed highways have legal names. Those legal names are the primary name. In order to quickly identify (and maybe some time in the future to provide route shields), the route number was included in the alternate name. This includes ramps, because sometimes it can be very confusing to see where a numbered route deviates from its obvious course.

This ramp is a perfect example. State Route 20 West splits off from Special Route 401, which continues north as a freeway to the airport. Unfortunately, with this latest change, drivers are no longer getting an "exit right" instruction which defies all logic and common sense. There really should be a ramp exclusion from the TTS logic.

I would really like to have some solid confirmation from WazeHQ that this is a permanent change and not subject to discussion before I go through the entire state of connecticut and re-work all of the alternate names we spent so many hours on. I can put quick fixes in as I identify them, but it seems like this is a code issue rather than a map issue.
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Re: [Page Update] How Waze determines turn/keep/exit maneuve

Postby pumrum » Mon Oct 13, 2014 3:05 am

PesachZ wrote:Make the first 5 meters of this ramp be a no name segment.


Of course there are probably 1000 ways to solve this particular issue. I'm not sure that breaking the ramp into 2 parts is my favorite, since that would break our numbered route continuity concept at which point I may as well just remove the alt name from the ramp as it exists now and not add extra junctions.

I guess the points I was trying to illustrate was:

1) aren't we supposed to avoid clobbering hacks into the map to circumvent fundamental issues with the software? I know that guidance has been handed down before, but I'm mobile so I can't locate it just now

2) why would you ever, in any circumstance want a ramp as a sole right branch from a continuous highway to NOT give an instruction? It doesn't make any sense to me at all, given my limited but growing knowledge of Waze. If anyone can think of a reason, I'm sure PesachZ (the turn instruction guru) can :)
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Re: [Page Update] How Waze determines turn/keep/exit maneuve

Postby qwaletee » Tue May 06, 2014 6:21 pm

Hi,

I think you may be misinterpreting the whole angle thing, since it is in fact badly written with not every use case (or piece of logic) converted. There's clearly a language barrier at work.

There are two major steps to the algorithm. The first decides whether the maneuver through the next junction should consider an instruction. The second decides what instruction that should be.

The 45 degree angle stuff is part off the second part. At this point, the routing engine thinks that an instruction is necessary, but has to decide what instruction that should be. The instruction it gives will be in relation to the straight ahead continuation ... aka Best Continuation. If the angle is bigger, left; smaller, right. There are additional factors that will determine keep/turn/exit, which include additional angle measurements and road types.

Unfortunately, it is not described well.

I would like this converted to a flow chart. Of Waze is not willing pit one of, we can create a Steadman and have them tell us where we got it wrong.

Just to give an example of how the angles work that may be counterintuitive. Say you have a girl in the road, but both forks are right of 180 degrees. The main road is bent at a 140 degree angle (call this northeast for simplicity). The branch is a few degrees right of center, call that NNE. Even though you have to turn slightly RIGHT to take the branch, the instruction is to keep LEFT, because it is left of the Best Continuation. That's the whole point of the best continuation, to provide a reference point compare to for right or left. It says nothing about how sharp the driver maneuver is.

Separately, for keep/exit/turn, it has to check the angle of the road you're on to the road you're going to, which determines how sharp the maneuver is.

That is my understanding of the algorithm. Due to ambiguous language and a few logic holes, I can't determine many additional details.
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Re: [Page Update] How Waze determines turn/keep/exit maneuve

Postby qwaletee » Wed May 07, 2014 1:41 am

Not evaluating the overall chart yet, just one point which I believe repeats an error that's always been in the description.

Most people do not understand the difference between INTERIOR ANGLE and TURN ANGLE. So when a branch instruction asks "is turn angle >45 degrees," many (most?) people will think the angle of the two lines s-in and s-out are 45 degrees or more. What it really means is (for right turns), is the angle LESS THAN 135 (sharper than a north segment going into a northeast segment).

We should really clarify that upfront and/or explain it both ways in the logic question.
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Re: [Page Update] How Waze determines turn/keep/exit maneuve

Postby qwaletee » Thu May 15, 2014 3:28 pm

Hi, PZ, good stuff. Yigal, anyone?
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Re: [Page Update] How Waze determines turn/keep/exit maneuve

Postby qwaletee » Thu May 15, 2014 6:16 pm

CBenson, whether it ha always worked this way or not, we're now saying that we have documentation provided by Waze which is untruthful, but which we have published, and we are attempting to replace it with knowledge gained form trial and error. The problem is that we can't really verify this, since we can miss pieces of the logic that only express themselves in ways we haven't noticed.

So, again, there is a place for Yigal, or another routing developer: To either provide the corrected docs, or to at least verify a draft document we write ourselves as being accurate and complete.
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Re: [Page Update] How Waze determines turn/keep/exit maneuve

Postby qwaletee » Fri May 16, 2014 7:41 pm

jondrush wrote:Waze has never correctly handled 3 segments leaving a segment. That was one of my motivations for requesting the "straight as possible" command. It was also in the best practices not to have 3-degmetns leaving a segment. Splitting them into two junctions was advised, so the commands are correct.


Splitting into two junctions might actually make the problem worse in some cases. You could get two keep right instructions instead of one, or a keep left instruction for one of the two right-leaning branches, or no instruction at all for one of the outside branches.

This advice seems incorrect. Perhaps what was meant was to see if using a pair of junctions helps in particular instances where there are problems with a 3-branch situation, and see which configuration works better.
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Re: [Page Update] How Waze determines turn/keep/exit maneuve

Postby qwaletee » Fri May 16, 2014 8:22 pm

sketch wrote:"Keep right then keep left" or "keep left then keep right" for a center option is less inaccurate than simply "keep right" or "keep left" with nothing further. A double "keep right" or "keep left" might be redundant, but it is not inaccurate. Accuracy is more important than avoiding redundancy.


Completely disagree. To a driver, "keep right then keep left" would mean "take the right hand branch, then look for your next left." It would not indicate center at all. It is simply inaccurate to describe a center choice as left then right or right then left.

Keep right then keep right for the most right hand branch would be also somewhat inaccurate, but is not so likely to result in a misunderstanding by the driver.
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Re: [Page Update] How Waze determines turn/keep/exit maneuve

Postby qwaletee » Tue May 20, 2014 4:04 am

I typically find the save problems in test areas are due to using a city that is too far away, Sometimes it warns you about it, sometimes it just fails to save.

Which test area? TX, AK?
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Re: [Page Update] How Waze determines turn/keep/exit maneuve

Postby qwaletee » Sun Jun 08, 2014 9:03 pm

I don't see a reason to keep the old page. Just overwrite it. This will actually provide better continuity, as anyone can look at the page history to see the transition.
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