Highway Off-Ramp Segment Question

[hmarian]

Hello,

I had some ongoing discussion with EECGeek about some of his recent edits that includes saving the tip of the highway off-ramp connection to a two way parallel road segments as a street, vs. continuation of the ramp.
He says that he is convinced that he read it somewhere in the forum, that this is how the end of the off-ramp should be, but since he couldn't refer me to the source, I'm asking those of you who know the answer to come and help us figure this out.

See the two examples below and please tell us which of the two is the right way connecting the tip of the off-ramp to the road.

Example 1

Example 2

Thanks,
Hagay.

[andrewkjs]

The route that goes from ramp -> street -> minor highway (https://www.waze.com/editor/?zoom=6&lat ... 3,60185374) might not work over long-distance routing, since Waze will try to stick to highway-type segments over a long distance. At least, this is what I understand from another forum post. Perhaps other experienced editors can chime in here.

[CBenson]

I agree with Andrew. Don't use street segments, use ramp or the same class of highway as the split road. So I would say Example 2 is better.

[rottielover]

mapcat bow tie?

[andrewkjs]

mapcat bow tie?

I don't think that's going to be necessary here. Bow ties are used to stop u-turns on cross junctions, but on t-junctions, you can set up the turn restrictions in a way to stop the u-turns from happening, which is already being done here.

[rottielover]

mapcat bow tie?

I don't think that's going to be necessary here. Bow ties are used to stop u-turns on cross junctions, but on t-junctions, you can set up the turn restrictions in a way to stop the u-turns from happening, which is already being done here.

That is one benefit, but the other benefit is allowing you to connect split roads to singles using a single junction point. It's just a thought.

Edit, I took a 2nd look. The turn restrictions are such that you can make a U-Turn if you were heading South on Keele and came to this "T" segment. (example 1). From the aerial image it doesn't look like a u turn would be allowed there, but I have no familiarity with Canada, you'd have to tell me if you would be allowed a U-Turn there. *IF* not, then the bow tie method would allow you to suppress any U-turns, and bring all the segments to one junction. Again it's just a thought, and I have no idea about the U-Turns at that location.

[hmarian]

Could someone explain the concept of bow ties and how is it related to the question asked?

Any other thoughts so we could reach conclusion on this?

Thanks,
Hagay.

[HandofMadness]

Could someone explain the concept of bow ties

[hmarian]

So what is the conclusion?
Using example 1 or example 2?

[ottonomy]

It seemed to me that the early consensus in this thread was that example 2 was better for routing purposes. Obviously, if U-turns are specifically allowed on the minor highway there at the intersection of the ramp, then a small two-way section would be needed there.

Since your question about the applicability of bow-ties is still up was the air, I thought I would take the time to confirm my own thoughts on that. I created some temporary example roads out in the sticks, so I could fiddle with turn restrictions and make useful screenshots without possibly messing up someone's hard work.

As andrewkjs said, a bow-tie is not necessary at a T-junction for controlling U-turns.

The off-ramp segments have permission to make their turns onto the highway:

Intersections12.jpg (40.03 KiB) Viewed 426 times

The southbound segment of the highway can have a left turn restriction to prevent it from using the short ramp segment to make a U-turn, but if it's not a T-junction, and another street is inline with the ramp, then the southbound highway segment needs permission to turn left onto that street. The median segment has to allow a lefthand turn going north, because that is one of the allowed turns from the off-ramp. So now you have potential U-turn routing from the map, and no way to prohibit it without also limiting a legal left turn:

Intersections34.jpg (40.56 KiB) Viewed 426 times

Enter the mapcat bow-tie. With it in place, you can give the off-ramp segment and the highway segments all the turn permissions they need, but specifically restrict U-turns where applicable:

Intersections56.jpg (40.59 KiB) Viewed 426 times

Does this make sense?