Junction style guide: ramp restriction inconsistency

[jhfrontz]

Understood --and my preference would be to delete them with wild abandon.

Can you suggest a re-write that indicates that there is not a consensus on whether or not such turn restrictions are necessary?

[daknife]

Reading through this thread I see no such consensus jhfrontz, rather just the opposite, the consensus is heavily in favor of the straight through restrictions being mandatory even when explicitly legal. The only silence I see is silence about just allowing straight thru travel to occur. In fact you are the only one to really speak for toning down the language recommending the turn restriction. Jason did agree that maybe we don't need to add them where there aren't problems, but pretty much everybody else has been strongly in favor of restricting straight through travel. And I also favor the restrictions. I still run across UR's where the restriction isn't in place where people got the off and on routing. I think I've seen on Map problem due to someone driving through a turn restrictions, versus dozens and dozens of UR's about off-on's.

Straight thru restrictions are a good thing because the penalty in the system isn't sufficient for it to work correctly. Nobody should every be given an off on route.

[jhfrontz]

Check the thread posted in the original message.


We have hundreds of intersections like this in Ohio. I've never seen a straight-through routing that couldn't be explained by faulty GPS receiver (or other user-specific app issues), "ghost" segments (or other map issues), or other transient problems.

We don't mark the restrictions in Ohio. Ergo, there is no consensus on doing so.

Jeff

[Edit: I think I'd be way less invested in this topic if someone could cite a recent conversation with waze staff that goes something like "yeah, there's a known problem in the routing engine that can cause that; go with a workaround until we get that ironed out". Otherwise, I can't help feeling like there's a bit of "cargo cult" driving this. ]

[MysticCobra]

I was a little confused because I was thinking of a different type of exit ramp/interchange. I don't know if there are fancy names (like bow-tie, clover leaf, etc) but these are the two different types that I think we are talking about.

The one I previously described from the I495 beltway in DC is here:
https://www.waze.com/editor/?lon=-77.15 ... s=64105547

The off-on I think you are talking about is like this:
https://www.waze.com/editor/?lon=-77.86 ... s=52402273

In the 495 example, it would makes sense that I was routed onto the exit ramp and back on if traffic is slower on the main lanes (which it often is).

In the second example, I don't understand why waze would route you off-on. It is obvious that the exit with the stop should take longer (unless traffic is at a standstill on the main lanes).

These are two different things, though. A GPS error would take your icon down that road after you didn't exit and then eventually correct itself once you pass the exit. I've seen this and no harm done. You had already driven past the exit. In the 495 example, waze determined that the exit was faster and told me to go that way. I did and it was faster. Again, no harm done.

Can someone describe the scenario where someone is routed off-on? Is it just for traffic jams?

[bz2012]

Can someone describe the scenario where someone is routed off-on? Is it just for traffic jams?

As I said earlier, I have seen URs posted in the middle of no where, in places that there would never be traffic jams.

Here is one where there were several URs complaining about being routed off/on.
intersection with nodes added to prevent 'off/on' routing.
https://www.waze.com/editor/?zoom=2&lat ... TTTFTTTTFT

I tried adding a bunch of nodes along the ramps.
I don't think it helped, but I don't see any URs there right now.

EDIT: I don't know what happened to the link. I thought I had put it there but just saw no link so put it now.

[jhfrontz]

It would be great if someone could post some current URs where this happening -- it's really tough to explain which of the various map issues was responsible for something that's happened a while ago (especially given the different back-end infrastructures and and features/bugs that have come and gone).

It would be even better if one of the "champs" could get a reading on this from someone who has actually seen code.


Jeff

[jhfrontz]

Just an FYI for anyone following along. Discussion of routing off and back on via ramps has also popped up over here, referring to this interchange. For the record, the path via ramps is 1082 meters, via the freeway is 1100 meters.

I just got around to reading this, where there is a post that says:

There's coding to prevent that type of routing if the city name is the same on all segment before, during and after the ramps. However, city names often change at those junctions, so the simple solution is to remove the city name and therefore remove all doubt.

So I'm having trouble seeing how the "put turn restrictions on straight-through to prevent ramp-routing" directive isn't further qualified for pathological cases. What am I missing?

And I've yet to see anything in response to this posting-- which suggests that if the city names are the same on the off/on-ramps, there will be no routing (yet another example of something else that is causing the bad routing).

[AlanOfTheBerg]

For reference, two or three weekends ago I received a route which included taking the off-ramp-to-on-ramp route on a standard diamond interchange in an area I thought I had restricted long ago. Maybe I did, maybe not. I was the last editor, but since turn restriction changes don't update the segment last updated data, there's no way to know. All involved segments of freeway, ramps, and overpass were all the same city name. The wiki guide is still correct and the reasons why we do this are still valid.

With more Wazers and more accurate traffic data, Waze is likely getting "better" at not doing this routing, but the fact remains that the code still allows it, even with no traffic impact, and that only makes it more likely to be routed like this when traffic on the freeway is backed up. This ramp-to-ramp route is illegal in many states, just like using parking lots to bypass traffic on a surface street.

[skbun]

With more Wazers and more accurate traffic data, Waze is likely getting "better" at not doing this routing, but the fact remains that the code still allows it, even with no traffic impact, and that only makes it more likely to be routed like this when traffic on the freeway is backed up. This ramp-to-ramp route is illegal in many states, just like using parking lots to bypass traffic on a surface street.

Someone in this thread asked how to 'reproduce the off and on' ramp issue, and I think I know of a good way to do it, because I've found a total of two off-and-ons exactly this way.

So I start in say, SeaTac, WA with my Waze client in hand. I tell it to navigate to Centralia, WA. The logical route for this is I-5 S.

It'll compute a route. USUALLY the first time, this is a sane, straight through on I-5 route down to there. Here's where it gets interesting.

If I tell it to calculate alternate routes with the route button, it'll often come up with something else that looks ALMOST identical but isn't. And specifically, what it usually finds is an off and on, sometimes on a diamond, sometimes on a cloverleaf slip road. I already found one of these on exit 120 (Fort Jones, fixed with a slip lane crossover that allows a cloverleaf U-turn but not the I-5 off-and- on), and when I did the alternate route test again, found another at 132A (which I haven't touched, and in any case I'm satisfied of what I'm saying). I was doing this at 2 AM local time, so traffic ain't the issue.

I would conclude that at least at the present time, it IS in our interest to prevent off-and-ons with segment building or hard turn restrictions wherever possible, because the routing engine isn't looking deeper than off-and-ons for alternates as it is now - I just demonstrated it. The routing server only has so many cycles, and it testing whether off and ons are faster is kind of a waste, right? Thoughts?

EDIT: Oh, and...if you look at exit 132A (Permalink: https://www.waze.com/editor/?zoom=3&lat ... TTTFTTTTFT ), all roads in this area having to do with the exit are in the city of 'Tacoma'. No changes to and from one city to another. So it's still trying the off and on even if the cities are the same throughout.)

[CBenson]

The name of the road changes from "I-5 S" to "I- 5 S" That is from without the space after the hypen to with the space after the hyphen. If the name remains the same waze shouldn't route this way.