| +/- highway=tertiary
A road linking small settlements, or the local centres of a large town or city.
The highway=tertiary tag is used for roads connecting smaller settlements, and within large settlements for roads connecting local centres. In terms of the transportation network, OpenStreetMap "tertiary" roads commonly also connect minor streets to more major roads.
Using this tag
Outside urban areas, tertiary roads are those with low to moderate traffic which link smaller settlements such as villages or hamlets. For quieter linking roads, consider using highway=unclassified instead. For busier through routes, use highway=secondary or greater instead, although note that outside heavily developed areas there may be no busier sort of road than this.
Within larger urban settlements such as large towns or cities, tertiary roads link local centres of activity such as shops, schools, or suburbs. Use only for roads with low to moderate traffic. For the quietest sort of linking, non-residential road consider using highway=unclassified instead. For busier through routes and main roads use highway=secondary or greater.
Tertiary roads also serve to move traffic away from narrower or quieter streets (represented by highway=residential or highway=unclassified) and onto wider arterial routes (highway=secondary or greater) more suited for heavier traffic. In a planned hierarchy they may be referred to as collector, or distributor roads, although this tag is useful for mapping any road network, whether planned or emergent. Use it for roads which either serve at this intermediate level, or simply those that form a more developed or well-used link in the hierarchy than the most minor sort of street or lane if there's not much planning or variation in the area you're mapping.
How to map
Map a tertiary road as you would any other highway=*: draw a simple Way along your GPS trace or the centreline of the road if tracing satellite imagery, and tag it with highway=tertiary. To describe the highway in more detail, add more tags.
Some useful combinations:
- name=name The name of the highway, for example "Skipton Road"
- maxspeed=number The maximum speed which is allowed on the road, for example "120" (in metric countries) or "50 mph"
- ref=reference code The reference number of the road, for example "R 372" or "C452"
- loc_name=local name The unofficial or local name for a road
- maxweight=number The weight limit in tonnes, for example "5.5"
- surface=* A description of the road's surface, e.g. "unpaved"
- width=number or est_width=number Width of the road in metres, e.g. "4.5"
- lanes=number The total number of car-sized lanes available on the road, regardless of direction. Normally "2" or "1"; if two cars going in opposite directions can pass each other safely without slowing or leaving the road, that's "2" even if there's no centreline.
- maxspeed=number Maximum legal speed limit, e.g. "45", or "30 mph"
|Australia||Other roads linking towns, villages and Points of Interest to each other and the secondary network. In South Australia, roads that are classified as a 'D' route under the Alphanumeric system use this classification.||Australian Roads Tagging|
|UK|| There is a corresponding official alphabetic classification matching OSM's "tertiary" tag fairly well: 'C' roads. Note that this official designation is rarely seen on signs. For the purposes of mapping, it's normally best to tag distributor roads according to their relative importance in the road hierarchy, as described above.
One rule of thumb for UK roads is that highway=tertiary works well for roads wider than 4 metres (13') in width, and for faster or wider minor roads that aren't 'A' or 'B' roads. In the UK, they tend to have dashed lines down the middle, whereas unclassified roads don't.
Always consider the road in its context too. Where it makes sense to do so, favour keeping the classification continuous on the map over strict adherence to physical criteria.
|United Kingdom Tagging Guidelines#UK roads|
- The UK Government Planning Portal Glossary defines these as "[r]oads that distribute traffic and bus services within the main residential, commercial and industrial built-up areas".
- The 'C' road classification is rarely publicized and frequently only used by local authorities, for maintenance and planning purposes. In England, responsibility for designating 'C' roads is usually vested in the county councils, each of which decides upon its own numbering system. A 'C' road crossing a county boundary will probably undergo a number change and may cease to be a 'C' road altogether. For more information, see Chris's British Road Directory: The Great C-Road Hunt