why no left turn at intersection

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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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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 SlowlySlowly » Tue Jan 28, 2014 2:42 pm

I recently returned to Waze after a few years. This scenario has arisen twice within my first two hours of driving. Both times instead of straight I was directed to make a right, a U-turn and another right. I spent quite a bit of time looking at the intersections in the editor before finding this thread.

If it happened to me twice in two hours of driving I imagine it has to be a very frequent occurrence. Probably not the best way to greet brand new wazers.

Of course a lot of people in my area drive this way, cut through parking lots and do other things that are considered bad form in the name of saving 30 seconds. Regardless of whether this is the fastest way to get through the intersection, should a navigation program be suggesting this route? Perhaps an aggressive driving mode is called for?
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Re: why no left turn at intersection

Postby Machete808 » Tue Jan 28, 2014 1:16 am

Agree that some adjustment to the algorithm is needed. We've been getting the same complaints about being directed the long way around, frequently to avoid a left turn.

Problem is, sometimes Waze is right, but sometimes the difference would be so minor that it's not worth the headache of doing all the extra turns, etc. Glad to hear they're contemplating some threshold, like a 30-second difference, before routing people people in some odd way.
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Re: why no left turn at intersection

Postby rgatland » Mon Jan 27, 2014 5:47 pm

At the risk of dog-piling on this problem, I have seen several reports that fit this model, and in fact, I have had Waze try to give me some strange routing around a particular intersection several times. Have we heard back from the Wave developers regarding a resolution? If this goes on too long, Wavers could get disenchanted and opt for another alternative to Waze.
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Re: why no left turn at intersection

Postby CBenson » Mon Jan 27, 2014 4:15 pm

Here is what appears to be another example.
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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 aplycon » Tue Jan 21, 2014 1:31 am

I have examples of this popping up in south Florida as well. I'm glad I found this thread to see how frequent this issue has been occurring. Hoping that CBenson's latest post from Waze staff will prove to rectify this routing issue. Waze should almost always chose the left turn. I think that the driver should make their own decision approaching a light to wait for a long-queued left or a right on red + U turn based on the traffic and their driving style. I drive more aggressively and may chose that right on red "shortcut" but most people I know (and when are my passengers) denounce that practice as impatient and risky.

UR from Jan 1 in Coconut Creek, FL:
[ img ]
That right turn + U turn adds nearly 1km to the route instead of just taking the left. How could that possibly be time-saving?
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Re: why no left turn at intersection

Postby bz2012 » Thu Jan 16, 2014 5:32 pm

And this one could also be a jolly driver post
[ img ]
WAZE wouldn't let him turn left despite the fact that the turns were enabled. I think he meant 'no J turn needed!' because Louisiana has been putting J turns in many places.
http://www.dotd.la.gov/administration/public_info/projects/j-turn/home.aspx

WAZE seems to have implement its own version of the 'J' turn.

I call it the 'Y' turns because it makes the drivers wonder 'Y'! :)
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Re: why no left turn at intersection

Postby bz2012 » Sat Jan 11, 2014 11:42 am

CBenson wrote:Waze staff has stated that they are addressing the circumstance when historic data creates unreasonable routes to cut time. It is acknowledged that many times, Waze prefers to continue straight, make a u-turn and turn right instead of just turning left in the junction just to save a few seconds. Very often this is perceived as a mistake and not as a time saving.

Waze is testing changes to the routing that will prevent such detours if there is under a 30 sec difference between the routes.

Thanks for taking the time to contact them about the problem.
Here is 'yet another example' of erroneous routing through a U turn rather than simply making a left turn.'
[ img ]https://www.waze.com/editor/?zoom=5&lat=30.44363&lon=-91.09093&env=usa&layers=TBFTFFTTTTFTTFTTTTTTTTTTTTTT
The 'faster' explanation often given makes no sense from the data we have available. Segment speeds for the avoided segment 15 m @ 36 kph vs the speeds for the 'recommended segments'
East Bound 33 m @ 22 kph, North Bound 10 m @ 32 kph, West Bound 31 m @ 3 kph. Clearly, the 'avoided path' should have been 'faster', based on total average segment travel times.

Perhaps the 'hidden data' on "wait time" would make it clear. It would be nice if the map editor displayed the wait time at the nodes involved at the time the UR was submitted.
Perhaps the User App could capture that information and pass it along so that it could be displayed along with the Problem Report.
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