User:Kartografer/Roundabouts/USA

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Understanding navigation instructions

Normal roundabouts give a ‘turn right’ / ‘continue straight’ instruction. Non-normal roundabouts give a ‘take the X exit’ instruction. This section will explain the difference between a normal and a non-normal roundabout.
A normal roundabout:

  • Will give you a ‘turn right', 'turn left’ or ‘continue straight’ instruction.
  • Has up to 4 nodes.
  • All exit nodes are aligned within "normal" range of the entrance node.

A non-normal roundabout:

  • Has 5 or more nodes (Ex. Each segment of a split road connects at its own node.)
  • Has irregularly placed nodes (this will be covered in the examples.)
  • Will give you a ‘take the X exit’ (with arrows around it) instruction.

A roundabout can be both normal and non-normal at the same time depending on your entrance node.
Some examples will help explain:

  • For the sake of simplicity, let’s look at a roundabout with three exits.
  • The angle of the segment approaching the node does not matter, it can be similar to any of the segments below, or anywhere in between.

Roundabout 2.jpgRoundabout 3.jpg

  • Each time you approach a roundabout from one of the three nodes, an imaginary X-Y axis is drawn: (1) with the origin at the center of the roundabout and (2) aligned to the entrance node.
  • Coming from node #1, this is how we see the roundabout:
Roundabout 4.jpg


  • Both exits 2 and 3 are within the normal range (90°±15° & 180°±15°).


  • Both exits will get an instruction to ‘turn right’ or ‘continue straight’.


  • Coming from node #3, this is how we see the roundabout:
Roundabout 5.jpg


  • Both exits 1 and 2 are not within the ‘normal’ range – both will get a ‘take the X exit’.


  • Note: even if one of these exits was within normal range, the roundabout itself will be ‘non-normal’ and all exits will get the ‘take the X exit’ prompt. The entire roundabout must be normal.