[Tagging] Deprecating mini_roundabout

[Paul Johnson]

On Wed, Oct 23, 2019 at 5:06 AM Florian Lohoff <f at zz.de> wrote:

> 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.
>

At a mini roundabout?  I mean, for all five of 'em we have in the US so far
(three of which are blocks apart from each other in a city near me,
basically the same thing as the UK version but turns the opposite direction
and has a decorative brickwork or orange island instead of a white one),
no, not really, I'd just expect to be told which way to turn and that it
*is* a mini roundabout.  The only thing I might do differently than a
regular junction would be a straight through movement, have it pipe up to
say "at the mini roundabout, continue straight on."  This largely to tell
me the two things I need to know offhand at such a junction:  Turns work
backwards than normal and all four ways yield to people in the
intersection, otherwise roll it, so I can expect people to stop but can't
count on it if I get there first.


> 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.
>

Could we get a link to this roundabout?  Seems like a potentially difficult
call, mostly because the only difference between a painted on median and an
all-"truck apron" median is basically like going over a driveway curb cut
and not a physical barrier.


> > 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
> traversable.
>

This differs from an all-way stop, which is just bad engineering for stupid
people by lazy traffic controllers.
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