Two-way Ramps vs. Routing [Split from WME Validator]

[dbraughlr]

Ramp segments like this are all over and will stay that way because there is no good reason not to.

The rumor was that two-way ramps have caused routing issues.

I don't know the history of the rumor and have no good way to disprove or prove it.

A test case is a two-way ramp of considerable length (say, one-half mile) connected to two short one-way ramps connected to the freeway. When the on-ramp is restricted (closed), does Waze route the wrong way for a short distance over the off ramp to reach the highway?

The problem is that if a turn is permitted onto a ramp, the ramp should lead somewhere. When the one of the two short ramps is closed, the two-way portion might have to be made one-way in the direction that is still open to prevent routing problems.
With a one-way ramp, the entire ramp is either open or closed; thus Waze never encounters a dead-end while traversing a ramp.

[dbraughlr]

There is a road that passes a fast food drive through and a small loop around the building for the actual drive through, causing the same endpoints problem.

That actually explains a lot. Waze avoids routing you in a way that bring you back to the same junction going in the same direction. Apparently, the bug is that when it reroutes you, it includes the junction that you already traversed (or that is the other endpoint of the segment that you are on); it shouldn't. But because it does, you cannot be routed around a loop.

[sketch]

What basis do you have to suspect that my understanding might be wrong?

Four and a half years on Waze and its forums have given me a pretty good understanding of how it all works.

An unsubstantiated rumor is not a substantial basis for a Validator warning.

[CBenson]

What's recent? I've seen it in the past three months. Not sure about the past two months.

Issues with two segments connecting the same two junctions goes back to the Cartouche days where the waze error codes could be solved by adding junctions to make sure that the same two segments didn't connect the same two junctions. Unfortunately waze staff has variously at different times told us that the extra nodes are not necessary and also told us to add them to "loop" roads to solve routing issues. There is additional discussion here, but its not so recent either.

[sketch]

Well, substitute "Primary Street/Minor Highway/etc" where I said "street" in my original question, then.

Yea, ramp looks good given what it's leading up to; I get what you're saying there. However, in the grand scheme of things, what I saw in those examples look to me like a road leading up to the actual ramps going on/off the freeway and is not actually part of the ramp itself.

Having the validator not highlight a two-way ramp just because of the examples that I've seen so far seems like a good way of increasing the chances of someone missing a two-way ramp that actually shouldn't be two-way, without actually providing any real benefit.

A minor or major highway used in these cases would look quite bad in the client, especially in night mode.

Making editing slightly easier is not a valid excuse for making such a change to the map. Perhaps "name on two-way ramp" would be valid as a Note, and that would do a better job of showing two-way ramp segments that were actually set that way accidentally.

[SuperDave1426]

Question: In cases such as those, wouldn't it just make more sense to make them two-way streets until get to the point where it actually splits into on/off ramps attaching to the freeway? Is there a reason why that stretch of road segment must be type ramp?

Not sure they have to be ramp, but they shouldn't be streets. If not ramp, they should be typed at least as high as the lower of the types that they are connecting so not to interfere with the long route pruning routines. But, ramps usually just look better to me in those examples to me.

Well, substitute "Primary Street/Minor Highway/etc" where I said "street" in my original question, then.

Yea, ramp looks good given what it's leading up to; I get what you're saying there. However, in the grand scheme of things, what I saw in those examples look to me like a road leading up to the actual ramps going on/off the freeway and is not actually part of the ramp itself.

Having the validator not highlight a two-way ramp just because of the examples that I've seen so far seems like a good way of increasing the chances of someone missing a two-way ramp that actually shouldn't be two-way, without actually providing any real benefit.

[GizmoGuy411]

Around me, ramps have small highway maintenance signs that define them as ramps. If there sole purpose is to serve the freeway, and there is no local name implying that is a street, then I would call it a ramp.


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[CBenson]

Question: In cases such as those, wouldn't it just make more sense to make them two-way streets until get to the point where it actually splits into on/off ramps attaching to the freeway? Is there a reason why that stretch of road segment must be type ramp?

Not sure they have to be ramp, but they shouldn't be streets. If not ramp, they should be typed at least as high as the lower of the types that they are connecting so not to interfere with the long route pruning routines. But, ramps usually just look better to me in those examples to me.

[SuperDave1426]

I would like to see "2-way ramp" removed from the error list for US.

Why? Where in the US is a freeway ramp ever two-way? <puzzled look>

https://www.waze.com/editor/?zoom=5&lat ... 79&env=usa

Thanks for the extra visual aid.

There's no reason for that small area to be packed with two 1-way segments. Added complexity with no added value goes against the stated Waze Goals. Ramp segments like this are all over and will stay that way because there is no good reason not to.

No argument there - in both cases, the road structure itself suggests a two-way road on the map.

Question: In cases such as those, wouldn't it just make more sense to make them two-way streets until get to the point where it actually splits into on/off ramps attaching to the freeway? Is there a reason why that stretch of road segment must be type ramp?

[SuperDave1426]

I would like to see "2-way ramp" removed from the error list for US.

I agree. Like them or not they exist. I can't provide a PL at the moment, but look at I-75 Exit 14 Elm Ave in Monore Michigan for one example for both N and S sides.

Just painted lines. No physical divider even.

I found it. Here's your permalink.

And, wow. Never seen 'em like that before. Ok, thanks for providing an example that answered my puzzled question.