[Page Update] Junction Style Guide

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Re: [Page Update] Junction Style Guide

Postby deeploz » Tue Jun 16, 2015 9:03 am

voludu2 wrote:I have made the change referenced above


Thank you.
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Re: [Page Update] Junction Style Guide

Postby DwarfLord » Mon May 05, 2014 2:34 pm

Is there a wiki that deals with junctions like this one in San Jose?

Screen shot 2014-05-05 at 7.24.51 AM.jpg
N 1st & Tasman, San Jose
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What makes this one interesting is that U-turns are allowed coming down N 1st headed SE and returning up on N 1st headed NW, but not from any other direction (the light rail in the midst of everything just adds flavor).

Some editors recommend bowties, others recommend shortening the cross-section segments to 9m or less for U-turns to be disallowed.

But mostly editors seem to deal with these by adding at-grade connectors for left turns and then setting turn restrictions appropriately. Some connectors are geometrically literal, similar to at-grade connectors for right turns; others are abstract, basically an additional straight cross section. The theory of operation is identical.

If situations like this are covered in a wiki I have missed it, apologies!
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Re: [Page Update] Junction Style Guide

Postby DwarfLord » Mon May 05, 2014 3:08 pm

kentsmith9 wrote:Isn't it covered under Bowtie Intersection?

Yes and no.

There is a thread here in which jemay and bgodette discuss a "short cross-section" technique that appears to prevent U turns while allowing lefts and at the same time preserving literal appearance more than a bowtie.

There is also a practice, increasingly common, of adding an at-grade connector for left turns in cases like this. In fact, both of the intersections used as examples of the "short cross-section" technique in the aforementioned thread have since been redone with at-grade connectors! (jemay said he spent a great deal of time perfecting the "short cross-section" approach at the Seattle intersection but that effort is gone now).

The bowtie section of the JSG makes no mention of these other approaches, but the at-grade left-turn connector in particular is becoming quite popular. It's not clear if that approach is deprecated or if it's just that nobody had thought of it yet when the JSG wiki was written.
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Re: [Page Update] Junction Style Guide

Postby DwarfLord » Mon May 05, 2014 3:32 pm

sketch wrote:...any examples of the "at-grade connector" type?

The thread I referred to above provides a couple...

Screen shot 2014-05-05 at 8.24.05 AM.jpg
Garden of the Gods & Northpark, Colorado Springs
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and

Screen shot 2014-05-05 at 8.28.55 AM.jpg
Mercer & Fairview, Seattle
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Perhaps there's a better term for these than "at-grade left-turn connector" but that's the first nomenclature that came to mind. I think it's what you're referring to, diagonal segments.
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Re: [Page Update] Junction Style Guide

Postby DwarfLord » Tue May 06, 2014 11:58 pm

qwaletee wrote:I've also experimented with "sharp angle geonode" bowties. They look much better on the map/app. For segments not on the route, they're almost invisible.

Are these documented anywhere? I am trying to visualize what you are referring to and not succeeding.
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Re: [Page Update] Junction Style Guide

Postby DwarfLord » Fri May 30, 2014 8:55 pm

Just a quick THANK YOU GUYS SO MUCH for exploring this!

There are a lot of split-road intersections out there, and a lot of different techniques for handling them. But it's been a struggle trying to understand the tradeoffs, whether some techniques are deprecated and others approved, and why. Any work to expand the wiki treatment of split-road intersections is greatly appreciated :D
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Re: [Page Update] Junction Style Guide

Postby DwarfLord » Tue Jun 10, 2014 12:47 pm

Regarding wayfinders for continuing on the same road, I have been assuming the following is well known but I have not seen references to it.

In limited testing I found that a change in the alternate name, or the appearance of an alternate name that wasn't there in the preceding segment, is enough of a segment-to-segment difference to trigger a voice instruction without having to change the primary name. This is especially helpful where street numbering makes it trickier to change the primary name.

My testbed for this behavior is here:

https://www.waze.com/editor/?lon=-121.9 ... s=79253420

I post it with trepidation, because it appears to work great. Routing gives a "keep right" instruction for traffic continuing right on Camden, the URs have dried up, selecting for house numbers selects all appropriate segments, house numbers can still be used on the final straight-ahead stub of Camden, and the client & live map don't show annoying wayfinder instructions. If it violates some rule of which I'm unaware (there are surely many) perhaps my posting it here will get it reworked :? ...on the other hand I would like to be sure people know about this option if they don't already.
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Re: [Page Update] Junction Style Guide

Postby DwarfLord » Sun Jun 22, 2014 9:56 pm

Would it be possible to discuss part of the wayfinder section in the Interchange subpage of the JSG? The wayfinder guidance says:
JSG/Interchanges Wiki wrote:A wayfinder is warranted in [case of] non-obvious continuations, where at least one "exit only" lane exists on the side of the road where exits are not normally placed (in a right-hand traffic country, exiting traffic is to the left and continuing traffic is to the right)
.
The way this is written, it suggests that all situations with a left-hand exit (in a right-hand-drive country) are by definition "non-obvious continuations" for the non-exiting traffic. Strict adherence to this wiki will result in continuation guidance in all situations involving a left-hand exit.

I would very much like to see us qualify this definition, at least for cases where a single lane exits to the left from a multi-lane highway without removing a lane. Otherwise, if we apply this guidance, Wazers will hear puzzling if not maddening instructions to keep to the right when all they need do is avoid an obvious exit. The guidance will cause drivers unfamiliar with the road to make unnecessary lane changes, possibly in heavy traffic.

Here are three examples of left exits. I have personally driven all of them many times and I can assure you that in each case the continuation is abundantly obvious. The SR-1S Highway 17N exit has an existing wayfinder for the continuation and the "keep to the right" voice instruction still throws me every time (and I know the road).

US-101S Coast Village Rd exit.jpg
Left exit example
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SR-17N Santa Cruz Ave exit.jpg
Left exit example
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SR-1S Highway 17N exit.jpg
Left exit example
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Re: [Page Update] Junction Style Guide

Postby DwarfLord » Tue Jun 24, 2014 12:53 am

sketch wrote:What do we make it, then? The goal is to write the rule in definite terms so that there are no borderline cases, or as few as possible. "Where at least as many lanes exit as continue, or where at least 2 lanes are exit-only"?

How about defining "non-obvious continuation" as:

An uncommon-side exit (left exit in right-hand drive countries, right exit in left-hand drive countries) where either
  • (a) the exit consists of two or more lanes;
  • (b) the exit consists of a single lane that is signed leading up to the exit as "exit only"; or
  • (c) the continuation consists of a single lane.
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Re: [Page Update] Junction Style Guide

Postby DwarfLord » Tue Jun 24, 2014 1:12 am

After I posted I realized the first two items applied to both kinds of exit, and the first item was redundant in light of the second. So, more global guidance for "non-obvious continuation":

An exit situation where either
  • (a) the exit involves one or more lanes that become exit only on approach; or
  • (b) the exit is an uncommon-side exit where the continuation consists of a single lane.


(EDIT: This needs more thought; I withdraw the suggestion and will mull it over)
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