Tag:restriction=no_u_turn
 restriction = no_u_turn
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| Description |
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A prohibition against making a U-turn 
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| Group: restrictions |
| Used on these elements |
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| Requires |
| Useful combination |
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| See also |
| Status: de facto |
| Tools for this tag |
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A no U-turn restriction prohibits a road user from making a U-turn – that is, turning around and proceeding in the opposite direction. A prohibition against making a very sharp turn may also be signposted as a prohibition against making a U-turn.
How to map
Identify the intersection at which the road user may not make a U-turn. Create a relation with the tags type=restriction restriction=no_u_turn with the intersection node as the 
via member and the immediately adjacent ways as from and to members. If the road is a dual carriageway, the via member is the tiny segment of the cross street that connects the from and to ways. Otherwise, the same way may be a member of the same relation twice, with the roles from and to=*.
You can add implicit=yes to indicate that the legal no U-turn restriction has no explicit signage on the spot, or that there is no legal restriction but a U-turn restriction is being mapped regardless, perhaps for practical reasons.
Optionally, tag the location of the sign indicating this prohibition as the appropriate traffic_sign=* value, for example, traffic_sign=DE:272 in Germany.
If U-turns are only prohibited at certain times or by certain vehicles, use restriction:conditional=no_u_turn. On the other hand, if U-turns are normally prohibited except by certain vehicles, use except=*.
A U-turn restriction relation only pertains to U-turns at intersections. In some places, U-turns may be prohibited along a specific stretch of road or within a specific zone. In these cases, some mappers have tagged the roadway with u_turn=no or no_u_turn=yes.
Examples
Vienna Convention
(right-hand traffic)
Vienna Convention
(left-hand traffic)
United States
Vietnam:
restriction:motorcar=no_u_turn
Software support
No U-turn restriction relations are widely supported among routing engines.
Even if a U-turn restriction relation is missing, a typical routing engine tries to avoid sending the user on a U-turn, since it does not know whether the road is wide enough or the vehicle is short enough to successfully make the U-turn. Moreover, it cannot be sure whether a U-turn is actually permitted or whether a U-turn restriction relation just has yet to be mapped.
See also
- restriction=only_u_turn – the opposite tag, requiring the road user to make a U-turn
- turn:lanes=reverse – allowing the road user to make a U-turn from a particular lane
- manoeuvre=uturn – clarifying that a particular movement is considered a U-turn, even if it technically does not resemble one