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a-b-street / osm2lanes

A common library and set of test cases for transforming OSM tags to lane specifications
https://a-b-street.github.io/osm2lanes/
Apache License 2.0
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Should we distinguish center turn lanes? #184

Open dabreegster opened 2 years ago

dabreegster commented 2 years ago

https://www.openstreetmap.org/way/185226351 (an alleyway) and https://www.openstreetmap.org/way/742718564 (a larger road with a center turn lane) both come up as

{
  "type": "travel",
  "direction": "both", 
  "designated": "motor_vehicle",
}

I'm starting to think center turn lanes are some edge case. They're not really travel lanes; you generally can't just drive through one of them in either directions. (Or they become a regular turn lane close to the intersection and cease to be a shared turn lane.)

I want to distinguish these two cases in A/B Street. In the short-term I can detect the difference based on the total number of lanes, but I'm wondering if we should consider a type = shared_turn or something

BudgieInWA commented 2 years ago

I wonder if the property turn: "left" is the right hint for A/B Street to look at, because you should be routing carefully down direction: "both" lanes anyway, and signs or markings that specify a turn also prohibit anyone from using it for anything other than a turn.

I think that the center turn lane should appear as a both ways travel lane with a marked turn, but it would be convenient to also be told that the lane matches what we would call a "shared turn lane".

droogmic commented 2 years ago

Another thing I thought about:

Do either of you remember suicide overtaking lanes? That is a third type of direction: "both"... (albeit a now extinct type).

in living streets: routing should be normal in centre turn lanes: routing should use it for waiting to turn across traffic in suicide overtaking lanes: routing should avoid using the lane at all!

dabreegster commented 2 years ago

I think you're both right -- we don't need a special new type here. The thing that more flexibly distinguishes all the variations would be the addition of lane-level turn restrictions. That's been on my mind to add, but probably not a priority yet.

Do either of you remember suicide overtaking lanes?

No, I had to look these up! I'm familiar with crossing the center line on some rural highways, but the idea of a lane meant for both directions to accelerate and overtake traffic sounds almost comically dangerous!