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]".
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.
tom
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