Key:traffic_signals:direction
 traffic_signals:direction
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| Description |
|---|
Indicates the direction of travel affected by the traffic signals. 
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| Group: highways |
| Used on these elements |
    |
| Requires |
| Useful combination |
| Status: in use |
| Tools for this tag |
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traffic_signals:direction=* is used with highway=traffic_signals to indicate the direction of travel affected by the traffic signals.
This tag only applies for nodes that are part of a way. For traffic signal nodes placed at their real position next to the road, use direction=* with cardinal directions or angles as the value.
Description
Complex junctions where multiple crossing nodes are tagged with highway=traffic_signals can cause routing algorithms to interpret two or more individual traffic signals where in reality traffic signals only apply once to crossing traffic. This can be overcome by tagging the direction of travel affected by the traffic signals.
Using this information routing algorithms can better determine how traffic signals at a junction affect journey time and provide better weighted route choices.
Tagging
| Key | Value | Element | Comment |
|---|---|---|---|
| traffic_signals:direction | forward | 
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Only traffic which passes in the same direction as the way is affected. |
| traffic_signals:direction | backward |
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Only traffic which passes in the opposite direction as the way is affected. |
Note that this tagging is ambiguous in case the node belongs to more than one highway=*! For this reason, use the traffic_signals:direction=* tag only on nodes which are part of exactly one highway. Avoid junction nodes and nodes between two ways as well (where they have been split, but are connected by a node). If in doubt, better simply insert a new node into the way which can be freshly tagged.
Rendering
The iD editor does render traffic_signals:direction=* by adding cones to the map. Attention these cones doesn't point to the direction of the affected traffic flow as defined above. These cones points to the opposite direction, which means in the view direction of the traffic signal (similar logic compared to traffic sign faces, bench and viewpoint directions).
See also
- Tagging of complex intersections for how to use these tags.
- highway=traffic_signals
- Forward & backward, left & right