When U-Turn Is The Best Choice

by **jasonh300** » Mon Dec 24, 2012 9:14 pm

This would be Waze using a dead-end as a U-Turn. There's not a whole lot we can do about it as editors. It's a bug in the system. Fixing self-connectivity doesn't help because it comes back as soon as someone drives on the segment.

Via my iPhone 3GS.

by **jasonh300** » Fri Dec 28, 2012 12:42 am

To be clear, the dead-end "u-turn" is a bug, not a feature.

Post a permalink of the area and give details about the route around that area and I'll try to duplicate the issue. If I can, I'll send it to the developers.

by **jasonh300** » Fri Dec 28, 2012 4:04 am

Well, in the second situation, fillippo disconnected two of the streets...I can't see what else he might have done.

In both of these cases, the routing server doesn't seem to have any other option besides to have you turn around on a dead-end. It's possible that the roads in question didn't have an end node, or had reverse connectivity and now that's fixed. There's nothing visibly wrong with either road, except the second one where that extra dead-end was disconnected. This is kind of a unique area where there's A LOT of dead-ends and very few loops. When you're heading the wrong direction, Waze wants you to be going the other way pretty quickly. When it can't find a way to go, it basically gives an error, but tries to recover from the error without crashing. The end result of this is routing onto a dead-end and bouncing back off the end. It won't give a turn-around instruction at the end. It's just going to give a "turn left onto..." and then the next instruction will be "turn right onto..." whatever road you started out on.

What it probably should do in these cases is make an announcement "Make a U-Turn where safe" and leave it up to the driver to find a place to turn around.

by **witfits** » Mon Dec 24, 2012 7:47 pm

When selecting a destination in which the best route requires a u-turn, the routing system suggests the next turn. If the turn does not have an outlet, it only recalculates when I reach the end point. Sometimes the end point can be a half mile or so. Further, you can end up where you'd rather not be. I am trying to understand what is going on. Is anyone else experiencing this? Any explanations?

by **witfits** » Tue Dec 25, 2012 5:35 am

Okay, but just to make sure... The route, and the route details include only the information up to the end point. It's not telling me to go to the dead-end and turn around. It isn't until I reach the end-point that it recalculates.

To me, if what I'm experiencing can be easily reproduced, and is actually what I'm describing (would like more data points to verify) then escalation should be in order.

To pile on; this happened during a drive that the system didn't recognize. So the "map issue" I dropped isn't something I can see (whole other issue). Further, in the comments of the map issue, I left my user name and asked that other editors leave it for me to research. I will PM to the area manager as well.

Comments?

by **witfits** » Fri Dec 28, 2012 12:11 am

Update —
The drive was added to my records. Drives are not necessarily added chronologically. Distance plays a factor into when the drive gets posted.
Unfortunately, the map issue was addressed but I cannot tell what, if any, fix was applied.
However, I did find this that may be helpful.
[url]http://www.waze.com/wiki/index.php/Creating_and_Editing_street_segments#Fix_the_end-node_on_cul-de-sacs_and_dead-ends
[/url]

I'm still not convinced on this issue of u-turns. Waze does not support u-turns. I'm not sure exactly what that means though. Am still searching for more information.

In order to disallow U-turns (in cases where the navigation might allow a sort of U-turn by making two left-turns) - the solution is to make the connecting segment shorter than 15 meters.

Unfortunately, at this time, there isn't a way to mark a U-turn as possible.

At large intersections, Mapcat Bowties are the best practice. But when on a two-lane highway the routing engine looks at two (2), or more left turns to make a u-turn. Still, I will continue to try and understand why we keep getting suggestions to follow a "no outlet" street when the best/fastest direction is to simply turn around.

by **witfits** » Fri Dec 28, 2012 2:49 am

1st situation — I was heading from Catlett Road toward Tyler Lane on Meetze Road. I punched in a navigation point that I knew would be shortest/fastest if I turned around. The system suggested I turn left onto the following permalink and took me down a dirt road, to a dark farm house, with very little room to turn around.
https://www.waze.com/editor/?lon=-77.70307&lat=38.61868&zoom=6&layers=BFTFFTTTFTTFTTTTTTTTTFT&segments=52421854
I sent rogitorius(3) a message asking what he/she changed but have not heard back.

2nd situation — I was heading from Maple Avenue toward Hughes Street on W Colonial Highway. I punched in a navigation point that I knew would be shortest/fastest if I turned around. The system suggested I turn right onto the following permalink and led me down to a cul-de-sac.
https://www.waze.com/editor/?lon=-77.67649&lat=39.13446&zoom=4&layers=BFTFFTTTFTTFTTTTTTTTTFT&segments=70258719
In this case, I dropped a "map issue" leaving my user name, asking if I could be allowed to investigate. It was edited by filippomorelli(1) so I don't know what he/she did.