Throughabout

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Consider the blue car: To make a left turn, you have to make a right turn first.


A throughabout

A throughabout (also known as “hamburger roundabout” or “cut-through” – http://en.wikipedia.org/wiki/Roundabout#Hamburger_roundabout) is a type of road junction that connects exactly one major road with one or more minor roads using a circled traffic. The major road is the one that passes through the circle traffic. Coming from the major road, you may not make a direct left turn. Instead, you have first to make a right-turn to leave the major road and enter in the circled traffic

Throughabouts can be quite small. In this case, usually they are not signal controlled; the mayor road has the right of way. However, they can also be quite big and have a lot of traffic signals.

In spite of their name, throughabout/hamburger roundabouts are not roundabouts. (No priority for the traffic in the roundabout and no non-traversable island). In this situation the tag junction=roundabout has to be avoided and junction=circular should be used instead.

How to tag (major road with single carrigeway)

Throughabout single carrigeway tagging.png

  • Major road
    • Tagging with highway=*
    • Applies to
      • way 3
      • way 4
      • way 5
  • Turn restrictions:
    • Tagging with type=restriction and restriction=no_left_turn
    • Applies to
      • relation with members/roles “from” way 4 “to” way 1 “via” node A
      • relation with members/roles “from” way 4 “to” way 2 “via” node B


How to tag (major road with dual carrigeways)

Throughabout dual carrigeways tagging.png

  • Major road
  • Turn restrictions:
    • Tagging with type=restriction and restriction=no_left_turn
    • Applies to
      • relation with members/roles “from” way 3 “to” way 1 “via” node B
      • relation with members/roles “from” way 4 “to” way 2 “via” node C

Which highway tag?

Example: The major road is “primary”. As minor roads we have some “tertiary” and some “residential”, so the circle traffic gets “tertiary”.
  • Major road: Normally, the major road has a higher highway=* key than the other roads. It keeps this attribute also when it goes through the throughabout.
  • Circle traffic: The hole circle traffic gets the highway=* key of the highest among the minor roads.