Should we distinguish center turn lanes?

[dabreegster]

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]

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]

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]

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!