Why divided roads are so bad

[ukemike]

Near my work, in Emeryville, California, there is a thoroughfare called Powell Street. In the map it is a divided road, because a mile to the East after Powell becomes Stanford, it really is a very divided road. But for the whole section called Powell there is no reason for it to be divided , and it causes problems. Where Powell meets Christie there is a user reported problem of a U-turn that is not allowed. But I can't figure out how to fix it. You are allowed to go through both ways on Christie, and all the various left turns are all allowed. So waze was telling the driver to make a left and make an immediate left (essentially a U turn). Based on the way it is set up now the same problem could happen on the other side of the intersection.

The only way I can see to fix this elegantly is to zip the whole divided road back together. That seems like it would be a lot of work to get even close to right, and if it was done half way it would be a disaster. Any thoughts? It would be nice if you could save a batch of modifications without applying them to the map. So you could do a large bunch of related mods, take your time, get it right, and then apply them all at once to the main map.

I don't know how to do hotlinks from, the map editor, so here is the location I'm talking about in that other mapping website:

http://maps.google.com/?ll=37.838691,-1 ... 19&vpsrc=6

[AlanOfTheBerg]

I have noticed that ALOT of roads in California are split when they shouldn't be. This is just a byproduct of the basemap import. I've spent many hours unsplitting them.

[harling]

...there is a thoroughfare called Powell Street. In the map it is a divided road... there is no reason for it to be divided , and it causes problems. Where Powell meets Christie there is a user reported problem of a U-turn that is not allowed. But I can't figure out how to fix it. You are allowed to go through both ways on Christie, and all the various left turns are all allowed. So waze was telling the driver to make a left and make an immediate left (essentially a U turn). Based on the way it is set up now the same problem could happen on the other side of the intersection.

Yep: if left turns are allowed from each road onto the other, U-turns will also be possible.

The only way I can see to fix this elegantly is to zip the whole divided road back together. That seems like it would be a lot of work to get even close to right, and if it was done half way it would be a disaster. Any thoughts? It would be nice if you could save a batch of modifications without applying them to the map. So you could do a large bunch of related mods, take your time, get it right, and then apply them all at once to the main map...

IMO, the only reason not to merge the road(s) into two-way roads is if the actual lanes are so far apart that it causes GPS tracking problems. (And even then, you can still prevent U-turns by merging both roads to single two-way segments, just where they intersect. It can look ugly, but at least it works.)

As for editing the map part-way, don't sweat it:

• Changes don't get published to the clients immediately, so you don't have to merge the entire roadway in one fell swoop. As long as you don't leave segments disconnected overnight, chances are nobody will ever see anything but the finished product.
• If you can't finish the entire road in one sitting, you can always connect the one-way roads to the merged two-way road wherever you have to leave off; just make sure the turn restrictions are correct.

[bgodette]

[ThunderTech]

I have a different perspective on Divided Roads.
When the roads are divided by a median that is 15 foot wide or greater, the roads need to be split.
I say this for several reasons...
I've noticed that when I stop at a drive-thru (while navigating) that Waze will show me being on a road that is near the fast food place where I've stopped. Some people blame this on the submarginal accuracy of Cell Phone GPS's, but Waze tries to snap to a road if it falls within a certain distance (don't know the exact tolerance) from the users location. I think that because many of the roads on Waze are not drawn more precisely, that Waze is forced to expand the road snapping distance. If the roadways were drawn with greater accuracy, then Waze could eventually tighten up on how far a user is off the road before showing them as being off the road.
I don't think that the majority of the GPS Receivers are that inaccurate in displaying current location. When I Pave a new subdivision, and then go to edit the map, I've been very surprised at how accurate the GPS Track overlays on the aerial photo. It will display precisely which side of the road I was driving on when Paving.
I've also noticed the majority of GPS tracks displayed on a map clearly show which side of the road users are driving on and it becomes even more prominent when the road is divided by a 15' wide median. (The width of a center turn lane)
If we improve our accuracy, then Waze can improve their tolerance as well and the numerous split road errors that occur due to folks driving through the McDonald's will become fewer. Many of the Split Road errors I see in cartouche (not to be confused with a Divided Road being drawn on the map, but an error where a person drove through a drivethru, and Waze snaps to a different nearby road as the car drives in the parking lot)
IMO, the U-Turn issue can be resolve by adding a new definition for road segment called "Intersection" which could be used to define a section of road that crosses a divided highway and where U-Turns are allowed. (Of course, there should also be a way to flag where U-Turns are not allowed as well)

[AlanOfTheBerg]

Sometimes parking lot/private roads are a good answer. 15 feet is a good number, and it aligns with the 5m guidelines found in the wiki, which was authored by Waze in this case, not the community. The median must be undrivable, though. Can't be a 15-foot wide turning lane.

[Scottie-Ice]

Hi all,

Slightly different situation. In San Francisco, there are many roads where no left turns are allowed for long stretches. I find that when a road is divided, even when I've disabled all the left turns in both directions, the navigation still directs people to turn left.

I understand that it takes some time for the "live" map to update after edits are made, but it's been at least 3-4 days, and in some cases several weeks.

Any thoughts on how to ensure the left turns are disabled so navigation won't direct people to make the illegal left turn, and/or how to get feedback on whether or not the live map has been updated? On some roads, I believe that it's probably OK to merge the divided highways, but in some places it may be difficult. Such as on Sunset Blvd, due to the width of the median... (See 1st link below.)

Or streets such as Octavia on the stretch near Market, which, has a median that's only ~10 ft wide, but adjacent roads are very close, so unsplitting the roads may cause GPS issues if the system has to debate if it's on Octavia Blvd or Octavia St. (2nd link)

Bottom line, if someone could help me understand why these left turns are being permitted by the navigation, I'd appreciate it. I imagine it has something to do with the divided highway, but can't figure why it's allowing the turns.

If I can figure this issue out, I should be able to resolve the majority of the main trouble spots in SF very soon!

Thanks!

Scott


https://www.waze.com/cartouche/?zoom=7& ... s=57596339

https://www.waze.com/cartouche/?zoom=6& ... s=57610091

[WeeeZer14]

Maps haven't been updated since Jan 13th, so edits from a few days or even close to a few weeks ago haven't made it to the live system yet.

[ukemike]

I have a different perspective on Divided Roads.
When the roads are divided by a median that is 15 foot wide or greater, the roads need to be split.
I say this for several reasons...

I don't disagree at all. About 150' from my front door is a clearly divided road, and trying to handle it as an undivided road would cause all sorts of problems. So perhaps the title of my original post is an over generalization.

The road that I posted about is a split road another mile or so to the East, and should be since it has a big median with cross roads that each have their own stop signs, quirks, etc. The section where it causes problems is not divided at all. Most of it is two lanes in each direction with a double yellow line as the divider. Some sections have raised curbs or jersey barriers as a divider, but no large median.

Oh, and the video above is great, I think that might be better than the way I was going to tackle it.

[ukemike]

So I decided to start zipping the section of road together and I found that the road is locked.