|Indicates vehicle occupancy requirements of a highway|
|Used on these elements|
|Tools for this tag|
The hov=* (tag is used to indicate vehicle occupancy requirements for a way. Access limitations of this type may be known as carpool, diamond, T2, or T3 restrictions depending on the locale.)
As with related keys hgv=* and bus=*, hov=* sets OpenStreetMap access permission for all lanes of that way, overriding whatever permissions may exist by default on that way, or have been set higher in the access permission hierarchy. If some lanes on the way are HOV restricted differently (for example, common on carriageways), hov=*, if used, should be supplemented with hov:lanes=* for per-lane access and restrictions.
For all possible values, see access=*. Most commonly used are:
- designated: The way is designated to high occupancy vehicles.
- yes: High occupancy vehicles are allowed. This by itself does not imply that other vehicles are restricted from using the way.
- no: High occupancy vehicles are not allowed on the way. This by itself does not imply that other vehicle types are allowed to use it.
lane: Deprecated and nonstandard. If seen on a way, this value should be removed; instead, hov:lanes=* is the preferred tagging for HOV access restrictions per lane.
- hov:minimum=* Typical values for this key are '2' (for "2+" lanes), and '3' (for "3+" lanes).
hov:lanes=* is used in cases where some lanes of a way have different HOV requirements from others. Lanes, the article describing tagging individual lanes of a road, fully describes how to do this.
As taken from the Lanes article, specifically regarding HOV lanes, "(hov:lanes=* is) most useful if entrance/egress is permitted at any point along the route; if entering or exiting the HOV lane(s) is only permitted at certain locations, modeling the HOV lane(s) as separate ways is preferable."
That said, here are two examples of how lanes might be tagged.
One driving direction
Without using permission inheritance
highway=motorway lanes=4 oneway=yes motor_vehicle:lanes=no|yes|yes|yes hov:lanes=designated|yes|yes|yes hov:minimum=2
This is a one way road with four lanes, where the leftmost of the four is designated for 2+ HOV traffic. HOV vehicles are allowed in all four lanes. Note that with highway=motorway, motor_vehicle=yes is almost certainly implied, so we must also restrict regular motor vehicle traffic from the leftmost lane. The motor_vehicle restriction, higher in the access restriction tree, is combined with the narrower hov allow permission, so '"all" motor vehicle traffic cannot use the leftmost lane, but HOV 2+ traffic is designated for it.'
Using permission inheritance
highway=motorway lanes=4 oneway=yes motor_vehicle:lanes=no||| hov:lanes=designated||| hov:minimum=2
In this case, we use the fact that highway=motorway has certain default permissions, specifically, motor_vehicle=yes, and hov=yes. We do not have to specifically tag the way with 'motor_vehicle=yes', nor 'hov=yes'. A lane whose access isn't specified (there is nothing between the two || symbols) will use the defaults, which in both these cases, are 'yes'. The two examples above are functionally identical.
Two driving directions
In the common case of two driving directions either
:backward is added to the end of the key.
oneway=no lanes=6 lanes:forward=3 hov:lanes:forward=designated|yes|yes hov:lanes:backward=designated|yes|yes hov:minimum=3
This is a road with three lanes in each direction. 3+ HOV vehicles are designated on the leftmost lane in each direction. Additional restrictions would have to be added for other vehicle types for these lanes, if necessary.
Please note that the lanes are viewed in the respective driving direction; i.e.,
hgv:lanes:forward describes the lanes in the same direction as the osm-way and the first lane-value refers to the leftmost lane in this direction, whereas
hgv:lanes:backward describes the lanes in the opposite direction of the osm-way and the first lane-value refers to the leftmost lane in that direction.
As stated above, please reference Lanes for a complete specification on how to perform HOV access restriction on a per-lane basis.
HOV lanes can be visualized during editing with the style Land and road attributes using the key hov:lanes=* and a lane-value of designated. The following screenshot shows a motorway tagged with hov:lanes=designated|yes|yes|yes|yes and hov:minimum=2.