United States roads tagging

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Road tagging by state

There is significant variation in highway construction standards, route signposting practices, and tagging conventions from state to state. This page provides a general national framework, but consult the appropriate state-level page for more locally relevant criteria and examples for highway=* and ref=* tagging:

Interstates

See detailed page on Interstates.

Motorway tag

highway=motorway applies to almost all Interstates, but a very small number of Interstates or segments of Interstates warrant a lower classification, such as highway=trunk. Any freeway anywhere in the United States, whether designated Interstate or otherwise, gets highway=motorway. Any ramps onto or from a motorway get highway=motorway_link.

Access onto a motorway comes exclusively through ramps (controlled access). A few private driveways and farm access roads emerge directly onto some officially designated Interstates in otherwise remote areas; even where these driveways lead into median breaks, they do not imperil motorway status. Most public roads that intersect a motorway or trunk highway through motorway links or trunk links get a designation no lower than highway=tertiary in all directions from the intersection.

Trunk tag

NOTE: The definition below is not commonly used; see the talk page. Many people use trunk to mean "expressway"-grade arterials with very few at-grade intersections (mostly in the East) or major non-motorway intercity highways (mostly in the West).

Most controlled-access highways without adequate speed or travel lanes or with obstructions should be designated highway=trunk. This designation applies, for example, to the two-lane Interstate 93 in northern New Hampshire. highway=trunk should apply to any segment, travel on which typically implies or necessitates clearing the obstruction. Any ramps onto or from a trunk highway get highway=trunk_link, even if they otherwise qualify for highway=motorway_link. Ramps leading into or from weigh stations, inspection booths, welcome centers, rest areas, and similar diversions accessible only from a trunk or motorway highway also carry highway=trunk_link.

Trunk highways include controlled-access highways that lie within military bases; contain draw bridges, toll booths, or other obstructions; have a speed limit less than 50 miles per hour; or have only one lane in each direction, whether divided or otherwise (sometimes called a "super-two" freeway). The designations highway=trunk and highway=trunk_link apply to all toll roads.

Primary tag

Green-signed interstate business routes, loops, spurs, and similar forks (and Interstate 180 in Wyoming) should be designated highway=primary unless they qualify for highway=trunk or highway=motorway. Access on primary highways may be uncontrolled; controlled-access segments of such highways merit highway=motorway (or occasionally highway=trunk) classification. When ramps link primary highways to highways of the same or lower classification, those links should be designated highway=primary_link, and those highways designated no lower than highway=tertiary. In no case should any Interstate highway receive any designation lower than highway=primary.

Examples

A typical one-route Interstate:

key value
ref I 95

A one-route named Interstate:

key value
name John Fitzgerald Kennedy Memorial Highway
ref I 95

A two-route Interstate:

key value
ref I 95;I 495

A two-route named Interstate:

key value
name Capital Beltway
ref I 95;I 495

U.S. Highways

U.S. Highway route information should be tagged on ways and route relations as follows:

Tag Ways Route Relation
network=* omitted
ref=*
  • ref=US 30
  • ref=US 30;SR 12 for concurrencies. For the sake of clarity, ascending numeric order within each network is recommended.
  • ref=US 30 Business
ref=30
modifier=* omitted
  • Omitted for main routes
  • modifier=Business or similar for bannered routes
name=* The name of the road; may or may not be present for numbered routes depending on local practice. If there are multiple names in use, use alt_name=*, loc_name=*, short_name=*, official_name=*, etc. Typically omitted for numbered routes, the route's name if there is a name such as "Ohio Turnpike"
description=* Typically omitted Useful description of the route, e.g. "US 56 Business (Herrington, KS)"

Application of Highway Tagging

The highway=* tag used for a U.S. Highway will vary based on the road's overall importance in the highway network. See the 2021 Highway Classification Guidance for information on determining which value of highway=* to set.

Former and Alternate alignments

Some U.S. highways have been decommissioned over the years; states occasionally post "historic," "old," or "former" on signs and maps. Historic US highways should be tagged with network=US:US:Historic on their route relations.

Examples

A typical one-route U.S. Highway:

key value
ref US 522

A one-route named U.S. Highway:

key value
name Washington Boulevard
ref US 1

A two-route U.S. Highway:

key value
ref US 50;US 301

National Forest Road System

The National Forest Road System[1] consists of more than 380,000 miles of roads within the United States, primarily facilitating travel through, or entrance and exit from, United States National Forests. They are operated by the United States Forest Service (USFS) and are officially termed National Forest System Roads (NFSRs).[2]

The Forest Service classifies roads into Primary Routes and Secondary Routes, with the latter type further subdivided by the style of its route marker. USFS also classifies roads by the level of maintenance they receive.

National Forest Primary Routes

Forest Route 90.svg

National Forest Primary Routes (also widely referred to as Federal Forest Highways or Forest Highways) are signed with a Distinctive Route Marker: this is a brown isosceles trapezoid, wider at the top, and with a scripted 'National Forest' or other similar designator on the sign. A Primary Route usually has a 1, 2, or (rarely) 3 digit numeric identifier which uniquely identifies it within the National Forest in which it exists.

National Forest Secondary Routes

National Forest Secondary Routes (also widely referred to as National Forest Development Roads, Forest Service Roads or simply Forest Roads) are signed either with a Horizontal Route marker, or a Vertical Route Marker. They have an alphanumeric identifier whose convention usually depends on the individual National Forest (such as 2464 or 22N45). This identifier may have additional letters on the end, indicating spoke roads off of the primary route number, such as 22N45A (the first spoke off of 22N45), or 22N45AC (the third spoke off of route 22N45A). The identifier is not necessarily unique, even within a single National Forest. Not all are signed.

Horizontal Route Markers

US Forest Service Horizontal Marker.png

National Forest Secondary Routes with a horizontal route marker are typically local collector roads signed with a white number on a brown brown background, with the number displayed horizontally.

Vertical Route Markers

US Forest Service Vertical Marker.png

National Forest Secondary Routes with a vertical route marker are typically the least significant roads in the National Forest road network. When they are signed, it is with the number displayed vertically on a brown signboard or post.

Maintenance Level

Each NFSR receives a maintenance classification, from 5 (most maintained) to 1 (least maintained).

USFS Maintenance Level Goal Notes
5 Offer a high degree of user comfort and convenience. Typically two lanes with a paved or compacted surface.
4 Moderate comfort at moderate speeds. Sometimes paved, but more often compacted aggregate.
3 For travel by a prudent driver in a standard passenger car. Comfort is not a priority. Unpaved, with moderate to poor smoothness.
2 Open for use by high clearance vehicles; not advised for passenger cars. Comfort is not a consideration. Unpaved, with very poor smoothness.
1 Closed to vehicle traffic. These roads are "in storage" and might be put back into use in the future. Basic maintenance is done to prevent undue damage. Unpaved, often overgrown. Should always be tagged motor_vehicle=no.
Forest Road 219B in Kaibab NF, with a vertical route marker and low maintenance level.

Most roads classified as Primary Routes have a maintenance level of 4 or 5 (generally well maintained for passenger cars). Most Secondary Routes with a horizontal route marker are maintained at level 3, 4, or 5. Secondary Routes that use a vertical route marker are usually maintained at level 1 or 2. It is also common for roads at maintenance level 1 to display no signage at all, in order to avoid confusion.[3]

Tagging Forest Roads

The following is a suggested tag schema for National Forest System Road ways:

Tag Description
highway=* secondary, tertiary, unclassified for Forest Highways

unclassified, service (eg. roads to parking lots, campsites and such) or track for Forest Roads

name=* (optional) The name of the road, if it has a friendly name. If it does not have any other designation but the National Forest one, the following is suggested:
  • Forest Highway XX (for those roads with a Distinctive Route Marker)
  • Forest Road XX (for any other National Forest System Road)
ref=* (required)

NF xx (for those roads with a Distinctive Route Marker)

FR xx (for any other National Forest System Road)

operator=* (optional) The name of the National Forest that operates this road (e.g. Okanogan-Wenatchee National Forest), or simply USFS.
access=* (optional) Any access restrictions on the way. Roads with a maintenance level of 1 should always be tagged motor_vehicle=no.

The following tags are also very helpful to map users, but they are difficult to determine without an on-the-ground survey or street level imagery. Add them if you are able to, but don't guess them based on the road's classification or maintenance level.

Tag Description
smoothness=* (optional) The smoothness of the road, which informs what types of wheeled vehicles will be able to traverse it.
tracktype=* (optional) Describes firmness of the road surface.
surface=* (optional) What the surface of the road is made of.

For route relations on Forest Highways and Forest Roads, these tags are suggested:

Key Value Discussion
type=* route Required. This is a "route" relation (as opposed to other types of relations)
route=* road Required. This route is part of the roadway network for automobiles (as opposed to a bus route, hiking route, cycling route, etc.)
name=* common name Required. The full name for this route. This will probably be in the format National Forest [Highway|Road] ###.
network=* US:NFSR:Forest name:NF

(or)

US:NFSR:Forest name:FR

Required. An example is US:NFSR:Chequamegon-Nicolet:NF for a National Forest Highway,

or US:NFSR:San Bernardino:FR for a National Forest Road.

Distinguishing the network in this way will keep individual National Forest Road systems distinct, and also allow for future shield generation corresponding at least to 'Distinctive Route Markers' and "other NFSR routes".

ref=* reference number Required. The alphanumeric route number. Examples: M3, 464, 22N13, 22N13AD.

Incorrect tagging

name=*

  • National Forest Development Road ###
  • National Forest Road ###
  • Fire Road ###
  • Forest Service Road ###
  • Forest Service ### Road
  • Fr ###
  • FR ###
  • only the identifier

Note: The TIGER import has incorrectly tagged most NFSRs as highway=residential, with their reference in their name, and ref unset. You can help the TIGER fixup effort by retagging these roads with a more appropriate highway classification, and fixing their name and ref tags.

Also note that maps and data published by the Forest Service includes many roads which should not be tagged using the Forest Road schema above. Do not use the Forest Road tagging schema for any of these:

  • roads that enter private land parcels within the National Forest
  • roads in urban areas
  • state and federal highways

Resources

Virtually every road operated by the United States Forest Service has an official reference number and maintenance level. These resources can help you find that information when mapping USFS roads in OSM.

Most National Forests publish a Motor Vehicle Use Map (MVUM). These can be used to determine a given way's name, reference, and maintenance status.

Also useful is the Interactive Visitor Map. The web map shows the road's name, identifier, and maintenance level.

Maps published by USFS, including FSTopo maps, or USGS maps. These maps usually make use of iconography that indicates whether a road is a Forest Highway (with a Distinctive Route Marker) or a Forest Road with either a horizontal or vertical route marker.

Please note that these resources may show roads that are closed to vehicles (maintenance level 1) or even abandoned. Forest roads tend to quickly become unusable due to forces of nature and sparse maintenance. Roads that have not been in use for a few decades may not exist on the ground anymore. Survey the road on the ground if possible (or consult satellite imagery and other resources online) and consider whether a lifecycle prefix such as abandoned:highway=* is appropriate. Assume that any road that appears on older maps but not in the MVUM or IVM is maintenance level 1 and therefore should be tagged motor_vehicle=no. Also consider checking if the road has been repurposed as a walking trail (usually with a different identifier). Other roads evident on the ground or from aerial imagery but not included in Forest Service data sources, may be "temporary" roads, firelines, or user-created routes and should be also tagged informal=yes.

Bureau of Indian Affairs, Power Administration, and Bureau of Land Management routes

These roads are found in Indian reservations, power administration (Bonneville, Tennessee Valley, etc) and BLM lands. The TIGER import has incorrectly tagged most of these ways as highway=residential, with their reference in their name=, and ref= unset. BIA routes should use relations, as the reference frequently carries beyond a single road similar to US or State highways.

key value
highway (required) unclassified, service, track, or tertiary depending on importance and status.
name (optional) Should equal the name of the road, if named.
ref (required) Should equal BIA (number), BLM (number), etc., where the number is equal to the way's road number.

State Highways

State highways should have a name tag, giving the street name, if any (e.g., "Elm Street"). This applies mostly where a state highway passes through an urban area.

State highways should have ref tags having as their values:

  • The two letter abbreviation for the state per the United States Postal Service's state abbreviation list, another abbreviation used by the state (such as SR for State Road), or no prefix. Different states may have different standards for which to use,[4] and there is no current inter-state standard.
  • A space.
  • The designation of the highway, be it numeric, alphabetic, or a combination.

The name and ref tags should not contain:

  • Cardinal direction designations (e.g., "N", "S", "E", "W"). Tag the cardinal direction on the route as described at Route directions, unless it is part of the official state route number.

Individual states

Please add your own state if you have information to add.

Delaware

Details of route signage in Delaware are related in Section 2D.11 ("Design of Route Signs") of the "Signs" section of the "Manual on Uniform Traffic Control Devices (MUTCD)".

Current state of key:ref values in Delaware

For state routes, only symbol shape should be used to designate that the route is a state route; neither "DE" nor "Delaware" nor "SR" nor "State Route" are to be added to the signage as a matter of this regulation. Examples of state route signs for Delaware can be found in Wikimedia Commons; for instance, for Delaware Route 18. As of December 2012, there is a mixture of "DE" and "SR" used for key:ref values, both often appearing on the same roadway.

Recommended state of key:ref values in Delaware

See Talk:United States roads tagging#Delaware ref values for discussion.

Texas

Texas has an extensive secondary highway network, with several numbering systems according to how the road connects with primary Texas highways. These include Loop, Spur, Farm-to-Market, and Ranch-to-Market, among many others. See the tables below for ref=*.

type of road ref= notes
Texas 6.svg (primary) TX 6 avoid tagging as "SH 6" or similar; it adds ambiguity
Texas OSR.svg Old San Antonio Road TX OSR only one route designated with letters; otherwise same as primary Texas highway shield
Texas Loop 12.svg Loop Loop 12
Texas Beltway 8.svg Beltway 8 BW 8 only one route designated as "Beltway"
Texas Spur 408.svg Spur Spur 408
Texas NASA Road 1.svg NASA Road 1 NASA 1 only one route designated as "NASA"
Texas Park Road 5.svg Park PR 5
Texas Recreational Road 10.svg Recreational R 10
Texas FM 3075.svg Farm-to-Market FM 3075
Texas RM 2381.svg Ranch-to-Market RM 2381
Texas RM 1.svg Ranch Road 1 RM 1 only one route officially designated as "Ranch Road"; otherwise same as Ranch-to-Market shield

Wisconsin

Complete information about how to tag ways and relations in the Wisconsin State Trunk Highway system in OpenStreetMap is available at Wisconsin/State Highway Relations.

Higher designations

If a state highway qualifies for highway=motorway, highway=trunk, or highway=primary based on the criteria discussed previously, then it should be so designated. Segments of state highways that join U.S. or Interstate highways generally should carry the primary or motorway designations, respectively, unless circumstances warrant a lower classification.

Secondary tag

Most state highways should carry highway=secondary. In rural areas, the secondary highway network connects towns and smaller communities to the outlying world. Secondary highways can provide access to higher-traffic local destinations, including some state and national parks, colleges and universities, military bases, major tourist attractions, airports, and facilities that employ several thousand or more people. Corporate driveways, however wide, should be designated highway=tertiary or highway=unclassified if accessed thorough traffic lights or links/ramps and publicly accessible but otherwise highway=service or dropped entirely.

Urban arterials with two or more lanes in each direction, generally with traffic signals but without stop signs, either a few miles or more in length or forming a network with other secondary, primary, trunk, and motorway highways, also usually qualify for highway=secondary. Arterial roads generally carry high traffic volume (near or more than 10,000 vehicles per day) near the highest speed generally allowed on surface streets (non-motorways) in the jurisdiction. A few urban arterials with significantly fewer interruptions at traffic signals and other obstructions and higher overall traffic speeds may be promoted to highway=primary; these highways can carry close to 100,000 vehicles per day.

A secondary road may exist as an arterial on a military base or within a military gate, where access is limited only or primarily to military personnel, their families, base employees, and similarly interested persons. Highways within military gates should carry highway=secondary and access=permit or access=private

Any way that serves as a circumvention of a traffic light or stop and is intended for turning or exit from a secondary road gets the designation highway=secondary_link oneway=yes, unless it leads to a primary or trunk road or a motorway.

Demotions

If the physical or traffic condition of a state highway or other road otherwise eligible for highway=secondary is inappropriate for such designation, then it may be demoted. Secondary highways generally should be paved and passable by on-road vehicles year-round (except perhaps seasonal closures in remote areas subject to extreme snowfall). Dead-end state highways that do not lead to towns or other locations justifying secondary designations and state highways inappropriate for travel with significant traffic volumes also may be considered for demotion, perhaps to highway=tertiary or highway=unclassified.

Example

key value
name Sycamore Street
ref WI 123

County Highways

These should be mostly highway=tertiary but will vary from state to state.

Oklahoma and other states generally may not number county roads. In Pennsylvania, these are quadrant routes and some other state-maintained highways (and occasionally bridges). In Texas, for example, farm-to-market roads or ranch roads constitute tertiary highways. Wisconsin and other states have networks of county highways. The Commonwealth of Virginia and other states number practically every road in the county. Open Street Map should carry those county highway tags, but that tag does not imply any tertiary highway status. Most paved roads in most counties should be labeled highway=unclassified (or highway=residential in urban neighborhoods).

Individual states

Please add your own state if you have information to add.

California

Imperial County Route S2 CA.svg California Scenic.svg

California unifies Interstates, US Routes and State Routes into a single numberspace, has an alphanumeric County Route system, subnetworks of Scenic Routes (in both the State Route and County Route systems) and two Historic Parkways (themselves a subset of the State Scenic Routes). See California/State_Highway_Relations#County_Routes.

New Jersey

Monmouth County Route 14 NJ.svg Bergen County Route 1 NJ.svg

County highways in New Jersey are divided into two groups, the '500 Series Routes' and individually assigned county routes. 500 Series Routes are coordinated by the state but maintained solely by the individual counties they traverse (except in cases in which they may multiplex with a state-maintained highway); with few exceptions, these routes are meant to cover long distances as alternatives to state highways and are contained within multiple counties. County routes designated within the individual counties usually have three-digit numbers beginning with 6 (or 7 if numbers beginning with 6 are used up) (Monmouth County and Bergen County do not follow this convention); there routes, with some exceptions (in which the number is usually carried over), do not cross county lines. Generally 500-series county routes should be tagged 'primary', and 600-series routes that cross county lines or link significant communities can be designated 'secondary' or higher depending on their importance or build quality. See the New Jersey page for more information.

Ohio

Map of Ohio counties with county route shield designs superimposed

Most counties in Ohio signpost their route numbers prominently; others either display plain route numbers on blade signs or small mileposts. A wide variety of shields are in use (see map at right). For the most part, these routes should be tagged highway=tertiary. There are, of course, exceptions. See Ohio#Tagging suggestions for Ohio and Ohio/Route relations/Networks for more information.

Oregon

County highways may or may not have a ref= tag depending on the county, rural counties are more likely to have refs than urban ones.

South Carolina

South Carolina uses three route numbering systems: Interstates, Primary Routes and Secondary Routes. The Secondary numbering system is unique within a county. The Secondary numbering system carries the county number followed by a unique number for that particular road. An example is S-40-100. This defines a secondary road in Richland County (40) with a road number of 100.

Route relation tagging for state highways / primary routes is as follows:

Typical highway - network=US:SC , ref=#
Truck route - network=US:SC:Truck, ref=# , modifier=Truck
Business route - network=US:SC:Business, ref=# , modifier=Business
Bypass route - network=US:SC:Alternate, ref=# , modifier=Alternate

Virginia

Virginia state routes are grouped into two categories: primary system(statewide); secondary system(countywide). Primary state routes are generally numbered below 600 statewide. Secondary state routes are generally numbered 600 and above within each county. Exceptions to the secondary system numbering within a county include I-664, state route 785 and state route 895

West Virginia

Main article: West Virginia § Road tagging guidelines
Circle sign 220-7.svg

County highways are sometimes signed with a fractional number. As an aside, do not simplify them into whole or mixed numbers!

Wisconsin

WIS County E.svg

There is an organized county highway system in the state of Wisconsin. For information about the system in general, see (Wikipedia): County Trunk Highways (Wisconsin). For complete information about how to tag the Wisconsin county highway system in OpenStreetMap, and a list of its relations, see Wisconsin/County Highway Relations.

Higher designations

If a county highway qualifies for a higher classification (for example, as highway=secondary because it serves as an urban arterial), it should be so designated.

Tertiary highways

The designation highway=tertiary generally includes the predominant minor roads in a county. This designation generally includes well-trafficked routes (generally at least 1,000 vehicles per day) in all areas, roads providing access to minor attractions or employers, and urban collector streets. Roads meriting highway=tertiary include most of those with a traffic signal, or to which any tertiary or higher classed road defer right of way (at a stop sign, traffic circle, or other traffic control device), and divided mostly low-speed roads in neighborhoods, industrial parks, or shopping centers that carry low-speed traffic.

If a state maintains (or its smaller jurisdictions maintain) a set or sets of county highways that do not include a majority of highways in each county, then those county highways are generally considered highway=tertiary.

Unclassified roads

Some states and counties number practically every road in the county. Most of these roads should be highway=unclassified, but those in urban neighborhoods should be highway=residential.

A road can be classified highway=track if the road is insignificant in the road network, for example: logging roads, agricultural roads, and roads that don't service anything of significant public importance. See the highway=track wiki for more clarity on its nuances.

Ohio

Many townships in Ohio signpost their routes prominently, much the same way state routes are signposted. These routes should generally be tagged highway=unclassified or highway=residential, depending on their accessibility and length. Route relations are useful for differentiating the many signage designs; see Ohio/Route relations/Networks for details.

Example

key value
name North Fond du Lac Avenue
ref CH V (or CR V)

Other Roads

Roads that do not qualify as tertiary roads should be tagged highway=unclassified, but those in urban residential areas instead get highway=residential. Dirt track roads, forest development roads, jeep trails, and roads not passable by all vehicles merit highway=track instead.

Roads through parking lots (or campgrounds), alleys, corporate driveways, and other special roads generally intended for travel to a particular destination get highway=service.

Ways on which most motor vehicle traffic is either legally or physically prohibitive get highway=path, or a more specific tag as appropriate. This category includes roads that normally function as hiking trails because of barricades opened only occasionally or rarely.

Tagging with relations

Ideally routes in North America will be tagged as relations. See Relation:route for the technical details on how relations work for routes in general.

OpenStreetMap Americana displays accurate route markers based on the network=* key on route relations. It is hoped that the Standard tile layer will someday adopt network=*-based route shields as well.

What this scheme has done is standardize where route modifier text belongs and what the network strings should look like. With this in mind, the following scheme has been proposed:

Key Value Discussion
type route (required) This is a "route" relation (as opposed to other types of relations)
route road (required) This route is part of the roadway network for automobiles (as opposed to a bus route, hiking route, cycling route, etc.)
name common name (optional; required if no number) A name for the road if it has no number (e.g. New Jersey Turnpike), or a name that disambiguates in the editor (e.g. I 10 (FL) rather than a bunch of relations that show up as 10). Other variations of Key:name are also permissible.
network network identifier (required if part of a route system) The route network the route is part of. Some examples:
US:I = Interstate signed highway network
US:US = US signed highway network
US:xx = Primary state signed highway network for state with postal code xx, such as US:WI for Wisconsin
US:xx:yyy = county routes e.g. US:CA:Santa Clara or US:WI:Outagamie
US:XX:yyy = State route including a modifier. E.g., US:TX:Loop, US:TX:FM
US:xx:(yyy) = Other state/local signed highway networks e.g. US:TN:Secondary, US:MO:Supplemental
Some route relations have the modifier added to this tag, while others have them on the ref tag. Route modifiers, if they exist, should be included here, e.g. US:WI:Spur or US:US:Alternate , and in the 'modifier' tag of the relation.
is_in:state=* State Postal Code xx = e.g. OH;KY for I-275 in Ohio/Kentucky. FL for I-275 in Florida.
ref reference number (required if network is specified) The specific route number in question; may be alphanumeric (e.g. I-35E would have a reference number of 35E).
Some relations have the modifier added to this, while others have them on the network tag. If a route modifier exists (Spur, Truck, Alternate, etc.) it should not be present in this key. Instead, it should be incorporated into the 'modifier' key, and the 'network' keys for the relation.
modifier type (optional) Some routes have a "tab" (officially a "banner") attached to the route number that distinguishes it from other, related routes. Usually the text of the attached tab should be used; common examples as per taginfo include "Alternate", "Business", "Bypass", "Spur", "Scenic", "Toll", "Truck". Note that these values are capitalized! If the modifier tag exists, it should also be incorporated into the network tag.
direction=* direction (optional) Divided highways (dual carriageways) may have two route relations, one in each direction. Usually the cardinal direction of the tab on the sign should be used; for example, northbound US 101 should be tagged north. Unusual directional tabs (e.g. inner, outer, or directions on the QEW in Canada) should be expressed in full. Note the signed direction may sometimes be the opposite of the true orientation of the route (part of westbound US 90 Business in New Orleans runs eastward; part of eastbound I-26 in Tennessee runs to the west); the signed direction should be tagged.
symbol url (optional) Should be the URL of a graphical representation of the route's symbol, ideally in SVG format. For example, Wikimedia includes symbols for many US, Mexican, and Canadian routes.
state proposed (optional) Indicates that the route has been proposed but is not yet built or signed. Such highways may also have modifier=future.
wikipedia Wikipedia Page Title (optional) The text of the Wikipedia page title discussing this route, such as Interstate 5 or Wisconsin Highway 54 Nominatim uses the wikipedia key to weight/rank returned search results, so if a page exists for the route, it's a good idea to include this.

Other tags may also be appropriate and may be included.

Overlapping route example

A named route may not overlap precisely with a numbered route. In this case, separate relations for each route should be used.

For example, the Wikipedia:Ohio Turnpike crosses Ohio. About 3/4 of the route overlaps with Wikipedia:Interstate 80, about 1/2 of the route overlaps with I-90, and about 1/4 of the route is part of I-76, but none of the numbered routes coincides exactly with the Turnpike and all three exist in more than one state.

So, in this case there should be a relation for the Ohio Turnpike (name="Ohio Turnpike", symbol=http://upload.wikimedia.org/wikipedia/commons/f/f5/OhioTurnpike.svg), separate (but overlapping as appropriate) from the I-76, I-80, and I-90 relations which should be specified as e.g. (network=US:I, ref=76, symbol=http://upload.wikimedia.org/wikipedia/commons/a/ad/I-76.svg).

A short named route (e.g. "Main Street" through a small town) should not be a relation; instead, the underlying ways should just be tagged normally.

References

See also