Throughabout

Consider the blue car: To make a left turn, you have to make a right turn first.The traffic rules may vary: The route B may be allowed or forbidden.

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 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 carriageway)

• Circle traffic
  • Tagging with oneway=yes and highway=* and junction=circular. Please do not use junction=roundabout on the circle traffic!
  • Applies to
    • way 1
    • way 2

• 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
    • if applicable: relation with members/roles “from” way 2 “to” way 4 “via” node A
    • if applicable: relation with members/roles “from” way 1 “to” way 4 “via” node B

How to tag (major road with dual carriageways)

• Circle traffic
  • Tagging with oneway=yes and highway=* and junction=circular. Please do not use junction=roundabout on the circle traffic!
  • Applies to
    • way 1
    • way 2

• Major road
  • Tagging with oneway=yes and highway=*
  • Applies to
    • way 3
    • way 4
    • way 5
    • way 6

• 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
    • if applicable: relation with members/roles “from” way 8 “to” way 4 “via” node A
    • if applicable: relation with members/roles “from” way 7 “to” way 3 “via” node D

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.