Key:turn

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Public-images-osm logo.svg turn
Zeichen 297.svg
Description
The key turn can be used to specify the direction in which a way or a lane will lead Edit or translate this description.
Group: Properties
Used on these elements
should not be used on nodesmay be used on waysshould not be used on areasshould not be used on relations
Status: approvedPage for proposal

Description

The turn=* key can be used to specify the indicated turn or merge direction for a way or lane. The key is predominantly used with the lanes suffix (turn:lanes=*) to tag indicated turn markings for individual lanes at intersections or other junctions. While turn lane markings are the most obvious method of indicating turn directions, the turn=* key can be used in any situation where a manoeuvre is signed, marked or otherwise implied by road markings.

In situations where the turn=* key is insufficient to map an intersection correctly (where there are complex lane connections or manoeuvres, or where the indicated turn doesn't represent the actual lane connections) the connectivity relation can be added to represent the exact relationships between lanes.

Indicated vs Restricted

The indicated turn for a lane or way frequently differs from the actual manoeuvre required, and does not imply any actual restriction on movement. Using the turn=* key will not prevent routing and navigation software from using lanes or ways for any particular route. At intersections where turn=* and turn:lanes=* keys are used, legal turning restrictions are expected to be correctly specified to allow navigation programs to calculate driver lane assistance properly.[1]

Identifying a turn indication

The shape and method of indicating turns vary significantly between jurisdictions, and even within the same road network. A turn can be indicated through a variety of means, including regulatory signs, turn markings, road geometry or other road markings.

When markings are not indications

An arrow pavement marking may be used for something other than a turn indication, in which case it is unnecessary or counterproductive to add a turn:lanes=* tag:

Signage which use arrows or other symbols to indicate sharp bends or turns is also not indicative of a "turn", and are best mapped using keys such as traffic_sign=* and hazard=*.

How to map

Ways

The turn=* key is used on the way or ways:

  • from the first indication via road markings, signposts or similar indications (including traffic being guided by solid lines into a particular turn, e.g. "turn pockets")
  • to the junction or the completion of merge.

Indicated turns by direction

On bi-directional ways, the turn indications for one direction of the road can be specified using the turn:forward=* or turn:backward=* suffixes. While not technically required, the turn:both_ways=* key can be used to explicitly indicate the indicated turns apply to both directions of the way.

One-directional ways

There is generally no need to apply a direction suffix to the key when specifying the indicated turns for a one-way highway. Using a direction prefix on a one-directional way is generally confined to situations where there are vehicle-specific direction restrictions, or alternating one-way highways.

Indicated turns by lane

Where the indicated turn differs between lanes on a way, the :lanes suffix is used to specify each lane's indicated turn (see Lanes for further details on the suffix). In short:
  • The key changes to turn:lanes=*
  • View the road in the direction of the osm-way.
  • Add the lane-values to the value, starting with the leftmost lane and ending with the rightmost. Separate each lane-value with a | (vertical bar)
Indicated turns by direction and lane
The direction and lanes suffixes can be combined to define the indicated turns for each lane in a specific direction for a way: turn:lanes:backward=*, turn:lanes:forward=* , and turn:lanes:both_ways=*
When using the ":lanes" suffix, the number of values specified separated by vertical lines (|) must match the number of lanes according to their direction.

Same indicated turn for all lanes

The turn=* key can be used without the :lanes suffix to specify the indicated turn for all lanes in a way. This usage is significantly rarer amongst taggers and is less supported by tools and data consumers that the widely adopted turn:lanes=* variant.
A majority of editors will use the turn:lanes=* tag even in situations where the indicated turns are the same for each way, or where there is only a single lane.
turn=*
turn:forward=*
turn:backward=*
turn:both_ways=*
turn:both_ways:forward=*
turn:both_ways:backward=*
turn:lanes=*
turn:lanes:forward=*
turn:lanes:backward=*


Values

A variety of indicated turn directions can be captured with the turn: key

These values can be used by themselves: to indicate that a lane or way can only make a particular turn; or combined with other values to create multiple turn directions for a way or lane.


If you specify multiple values any one of separate lanes, the lanes order must be preserved and must still be separated by vertical lines. A lanes tag whose value is given as turn:lanes=a1;a2|b1;b2 specifies values for two lanes, not three, each lane having two values, and is equivalent to turn:lanes=a2;a1|b2;b1 but not to turn:lanes=a1;b2;a2|b1.

by separating them with a semicolon (;).

Value Description Road marking example Signpost example
none, or (empty) there are no turn indications on this lane.

An empty value can be used in place of none (e.g. ||right is equivalent to none|none|right.) Both options are valid, though some mappers prefer the explicit none value for better readability

N/A N/A
left left turn Richtungspfeil Links.jpg France road sign B21c2.svgFrance road sign B21-2.svgMUTCD R3-7L.svgMUTCD-PR R3-7(I).svg
slight_left slight left turn
sharp_left sharp left turn
through going straight through Richtungspfeil Geradeaus.jpg France road sign B21b.svg
right right turn Richtungspfeil Rechts.jpg France road sign B21c1.svgFrance road sign B21-1.svgMUTCD R3-7R.svgMUTCD-PR R3-7(D).svg
slight_right slight right turn Autobahnkreuz A24 - A10 bei Potsdam - Leipzig - geo.hlipp.de - 3191 crop.jpg
sharp_right sharp right turn
reverse reverse/U-turn U turn A2 Lithuania.JPG
merge_to_left the traffic of this lane has to merge with the traffic of the lane to the left of it US "right lane ends" sign
merge_to_right the traffic of this lane has to merge with the traffic of the lane to the right of it US "left lane ends" signFahrbahn 2.pngFrance road sign C28-3.svgNederlands verkeersbord L5.svg

Turn Combinations

left;through / through;left left turn & through (only) (the variant of used values is to be discussed, see table of some distribution examples here: distribution) Turn-left-through.png
right;through / through;right through & right turn (only) (the variant of used values is to be discussed, see table of some distribution examples here: distribution) Turn-through-right.png

Rarely Used Tags

More complicated or unique turn indications can be mapped using user defined tags.

There is turn:lanes=slight_left|slight_left;slide_right|slight_right mapped once, this is sole case of turn:lanes=* value containing "slide" text[2].

slide_left slide to left. Note: This is a new tag that is hardly ever used. You can create a similar tag with a more appropriate name
slide_right slide to right. Note: This is a new tag that is hardly ever used. You can create a similar tag with a more appropriate name


Examples

Motorway with links and destinations

The following example shows a motorway with two links.

TurnExample6.svg lanes=3
TurnExample5.svg lanes=4
turn:lanes=none|none|none|merge_to_left
TurnExample4.svg lanes=3 (lanes=1 on ramp roads)
TurnExample3.svg lanes=4
turn:lanes=none|through|through|slight_right
TurnExample2.svg lanes=3
turn:lanes=none|none|through;slight_right
destination:lanes=A|A|B
TurnExample1.svg
 
A3-Ring-StevensWoluwe.jpg Klettenberg, Köln, Germany - panoramio.jpg lanes=4
turn:lanes=through|through|through|slight_right


Example for a one-way

There are three lanes on a one-way, and the leftmost lane will turn left, the rightmost lane will turn right and the lane in the middle will go straight through the next junction.

 turn:lanes=left|through|right

Example for a road with both directions

There are two lanes on the road in each direction. Those lanes running in the same direction as the osm-way are considered to be "forward"; the others "backward". The left lane of the forward direction will turn left and the right lane will go straight through and also turns right. The left lane of the backward direction will go straight through, the right lane will turn right and also continue straight through.

 turn:lanes:forward=left|through;right
 turn:lanes:backward=through|through;right

Special turn indications for specific vehicle types

In some cases, some vehicles—typically buses or all psv vehicles or bicycle or taxi will have special turn indications.

turn:bus:lanes=* / turn:psv:lanes=* / turn:bicycle:lanes=* / turn:taxi:lanes=* may be used for such tagging.

As with other :lanes tags vehicle type is added before ":lanes" part (e.g. hgv:lanes, see Lanes).

Editor support

JOSM

iD

Adding a visual turn lane editor to iD was stated as planned during July-August 2016.[3]

Data consumers

Quality assurance tests

See also

References