[Tagging] Deprecating mini_roundabout

Florian Lohoff f at zz.de
Wed Oct 23 10:05:43 UTC 2019

On Wed, Oct 23, 2019 at 12:00:13PM +0200, Tom Pfeifer wrote:
> On 23.10.2019 11:35, Florian Lohoff wrote:
> > > These are a very common feature, it does seem odd that routers are not supporting them.
> > 
> > The point is that a mini roundabout does need a LOT of preprocessing to
> > put it into some graph for your classical A* or Dijkstra. You need to
> > eliminate the node and replace it with a circular road much like a
> > junction.
> Could you explain what the preprocessing is needed for, and why you need to
> replace it in the routing algorithm.
> From my perspective nothing is needed. The routing engine recognises from
> which way you come and where to leave, and, since the feature is so small
> and clear, it can give instructions like at a normal junction, just using
> the tag to describe the junction:
> "At the mini-roundabout [turn right|go straight|turn left]".

You would expect (as you see a roundabout sign) to get instructions to
take the n.th exit.

The roundabout change which triggered this mail is MUCH larger - And you
physically can go straight but there is a small curb - so cars will use 
the circular road, trailers will possible use the curbed center with the
last axles.

> Basically the mini-roundabout is effectively more about who has priority,
> and here all incoming roads have to 'give way'. Similar a four-side "stop"
> sign in the US. I have used them in Britain and they are often just a bucket
> of white paint poured in the middle of a junction.

A mini_roundabout has the same rules as normal roundabout from what i
look at the definition. The only difference is that its physically

Florian Lohoff                                                 f at zz.de
        UTF-8 Test: The 🐈 ran after a 🐁, but the 🐁 ran away
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