why no left turn at intersection

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Re: why no left turn at intersection

Postby slandrum » Wed Jan 29, 2014 11:48 pm

Here's a permalink that contains a UR of right then U then right instead of straight.

https://www.waze.com/editor/?lon=-117.7 ... TT&env=usa
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Re: why no left turn at intersection

Postby slandrum » Wed Jan 29, 2014 7:08 am

I've seen right then U instead of left, straight then U then right instead of left, right then U then right instead of straight, and lots of variations of around the block routing. One that I encounter myself about once/week is a straight then U then right instead of left.

Whenever I encounter this, traffic is heavy or has been recently, but generally hasn't been heavy for more than 1/2 hour. Waze is seeing that the left turn is slow, but has no idea that the U-turn it's asking me to make will be even worse. Depending on the light cycle, I can sometimes make the left before I could have gone straight, but that's just timing when I reach the intersection.
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Re: why no left turn at intersection

Postby slandrum » Tue Jan 28, 2014 5:36 pm

This is now a very frequent occurrence, and I see several reports of it a day now, and run into it myself about once/week. I don't bother adding links to more examples to this thread, as there are plenty to understand what the problem is.
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Re: why no left turn at intersection

Postby slandrum » Tue Jan 21, 2014 9:13 pm

Daily I come across several more examples where instead of left turn, it wants to go straight through and U-turn back, or do a right, then a U-turn. And fairly common now popping up are instances where instead of going straight, Waze directs to take a right turn, then U-turn, then right again. This type of routing glitch seems to be getting more and more frequent with time. It suggests that either there's a serious problem with the routing engine, or there's a fundamental problem with the current concept of how Waze gets and uses speed information to make its decisions. When traffic gets heavy at an intersection, infrequently chosen alternates are going to start looking more and more appealing to Waze, and because no-one in their right mind would take them, Waze is never going to get a lot of data to refute it's ideas. Waze's problem is that it has no eyes, and can't see what's happening. It's information is indirect and incomplete. It can tell to a limited extent what the drivers do, but cannot tell any information about what they don't do, and has no concept why not. Waze doesn't even really respond when Wazers refuse its instructions, eventually it may raise a flag for someone else to look at, but that's very far removed and indirect, and is not at all responsive to the current situation.

Waze also has a lot of trouble getting good timing data for turns on divided roads. If you are directed to make a left turn at the intersection, you aren't going to turn left at the end of the segment leading up to the intersection, you are going to turn left in the segment in the middle of the intersection. That segment will almost always have good time, because you don't enter the intersection unless you are going to clear it (if you are obeying the law in the US). The backup you have waiting for the light, however, will get lumped in with the straight through traffic, polluting their data making Waze think it's slower to go straight, and the straight through data will pollute the left turn data making Waze think it'll be faster to turn left than it will. This timing data is improved if the intersections are changed to bowties, but that introduces other problems.
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Re: why no left turn at intersection

Postby slandrum » Thu Jan 09, 2014 5:43 pm

Hopefully this is implemented soon. In the last couple days I've found at least a half dozen URs for this type of routing. It seems to be getting more and more frequent.
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Re: why no left turn at intersection

Postby sketch » Fri Jan 31, 2014 7:30 pm

Just as a matter of forum etiquette, it's best to avoid double- or triple-posting at the end of a forum thread. There are cases where it might be desirable, such as in a thread a couple days old when you have new information that needs the attention of the thread's subscribers. In this case, we're just compiling a list of examples, so if you have the last post in the thread it's better to edit that post to add more examples.
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Re: why no left turn at intersection

Postby sketch » Fri Jan 31, 2014 4:43 pm

I think the Service Road type is related to these issues.

See this thread: https://www.waze.com/forum/viewtopic.php?f=237&t=72818
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Re: why no left turn at intersection

Postby sketch » Wed Jan 29, 2014 1:49 am

Feel free to post those, too. Since the UR is all we have to go on in those cases, ask the reporter for more information and leave a note in your question asking other editors to leave it open.
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Re: why no left turn at intersection

Postby sketch » Wed Jan 29, 2014 12:46 am

Champs have to submit each occurrence manually, so the best data is gonna come from things you personally experienced. If any of y'all come across one of these yourself, leave a UR and make note of the time/date and your approximate route at that time, then post all that here, if you like.
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Re: why no left turn at intersection

Postby sketch » Tue Jan 28, 2014 11:20 pm

Staff have actually been collecting data about specific occurrences of this, not sure how much they need, but it seems the more the better. Staff are currently working on a prevention mechanism for this type of thing.
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