Highway Tag Africa
Typology of Road Network in African countries
From the experience with the Activations in various countries, the Humanitarian OpenStreetMap Team community has developed this classification of roads more adapted to the context of African countries. Before you make modifications to this page, you are invited to come and discuss on the HOT Discussion list
The road conditions in African countries do not always correspond to their economic and social role. A road typology should be based on the road importance and not on the surface or the visual appearance of a road. In some areas, major roads are unpaved and heavily damaged during the rainy season. It is important for remote mappers to adapt to this reality. In some areas, such as the Sahel, it is also important to consider the density of the road network.
This proposed typology for African countries is based on mapping experience in various countries, observations and discussions. In some areas, there is a very dense network of roads with many tracks going in all directions. In such a context, it is important to have a hierarchy of roads that highlights the more important ones for economic activities. highway=tertiary is used to highlight roads interconnecting with regional service towns. Also, highway=unclassified is used to distinguish rural roads interconnecting villages from tracks going to the outskirts of villages. If you're in doubt of what tag to use, use highway=road, keeping in mind that many highways are formed by repeated foot and animal traffic.
The individual mappers should classify a particular road when adding it to the OSM database. Once the network of road is completed, we have an overview of the road network, and experienced mappers can then revise this network and ensure that the hierarchy of major roads is clearly established.
This is open to suggestions, please share your experience/practices from other countries. To communicate, use the Hot mailing list.
The Highway tag reflects the Economic and social dimension of the road.
|highway||motorway||A restricted access major divided highway, normally with 2 or more running lanes plus emergency hard shoulder. Equivalent to the Freeway, Autobahn, etc.|
|highway||trunk||A main road with a motorway-like layout which is restricted to motorised vehicles. Other than motorways, trunk roads might have crossings or traffic lights.|
|highway||primary||The main axes connecting the big cities.|
|highway||secondary||The roads connecting with regional capital cities and the towns of some importance (health services, commerce, etc.).|
|highway||tertiary||The roads interconnecting villages and the major streets in towns of some importance.|
|highway||residential||Used for roads in the residential areas except the major streets that interconnect with various roads (ie. primary, secondary, tertiary).|
|highway||unclassified||The roads serving for interconnection of smaller villages and hamlets.|
|highway||track||The small roads going outside the residential areas, mainly for agricultural and forestry purposes. Tracks can also be found in National Parks and Game Reserves. In general these roads do not have connecting function with other roads.|
|highway||path||Paths not large enough for cars and mainly for pedestrians, both inside and outside residential areas.|
Road surface status
One can indicate the physical surface of the road with the surface tag:
Generically, a hard surface (asphalt, cobblestone, concrete...) is indicated with surface=paved and a soft one (ground, sand...) with surface=unpaved.
By default, primary/secondary/tertiary/unclassified/residential and service highway=* are supposed to be paved. If it is not the case, one must mention it, especially if the surface is soft. When potholes represent more than 50% of the surface, the way may be considered as unpaved.
In addition to surface material, on can indicate "viability" or "roughness" of the road with smoothness=*. This should help determining which kind of vehicle may use the road or the track.
|good||Usable with racing bike|
|intermediate||Usable with city bike, sports cars, scooter...|
|bad||Usable with trekking bike, "normal" cars. One can not exclude potholes.|
|very_bad||Usable with car with high clearance. Typically with 404 bachée. "Normal" cars can't go through.|
|horrible||4Wheel drive only.|
|very_horrible||4Wheel drive cars can't go through or it is very difficult, with help of winch. Usable with tractor, ATV, motorcycle, zebu carts.|
|impassable||No wheeled vehicle. Road damaged for instance.|
A suggestion would be to smoothness only when it is equal or lower than bad.
An approximative closing period can be provided with a conditional restriction :
access:conditional=no @ Dec-Apr: this track is usually closed from December to April (or open from May to November).
For the more complicated case where a track may be usable by 4Wheel drive car during dry season but only with zebu carts in rainy season, the following scheme is suitable:
When a road is crossing a river, whatever it is with a bridge, an organized ford ("radier", "baden") or natural ford, it should be tagged on the portion of the road affected. If the crossing section is too small (or difficult to separate the two ends), we put the information only on one point.
Bridges are tagged by default with bridge=yes and they should always also have a layer=1 tag. Practically the only case where another bridge=* value is used is when the bridge is very low (ie. has a low profile) and is regularly submerged under water during floods or rains. In such cases it should be tagged with bridge=low_water_crossing.
In addition to the surfaces described above some bridges have (wood) beams oriented in the drive direction so that there is only two narrow ways for the wheels. It is a problem for bicycles and motorcycles that can not cross such bridges:
surface=wood:lanes if beams are made of wood
As noted above some lower profile bridges are built intentionally so that they are submerged during floods or rains and are tagged with bridge=low_water_crossing. This tag alone implies that the bridge may be submerged at times but the flood_prone=yes tag is good to add also on these for clarity.
In some cases there is an alternative way for the crossing near the bridge. Such crossings (whether they be for trucks, bicycles or motorcycles -- or even regular cars) should be mapped. They involve a ford (ford=yes) in almost all cases. A number of these crossings are built intentionally -- even if the ford itself would be a natural one -- not only for trucks (when the bridge is too light-structured for them) or two-wheelers but also simply as an backup passage for all vehicles in case the bridge might be washed away in more severe floods. This is why such alternative crossings are important to map!
Fords: River or water crossings without a bridge are fords and should be tagged with ford=yes. This applies to both natural and constructed ("organized") crossings. depth=* allows to indicate the usual (dry season, out of flood or hurricane) depth of the water. depth=0 will be used for crossing usually dry but that may be used upon water. In opposite, a crossing usually dry that become dangerous to use once water is flooding should be tagged as flood_prone=yes. surface=* can be used as usual. A constructed/"organized" ford is often made of concrete and should be tagged surface=concrete, accordingly.
Note that if any structure exists that allows normal level water of any waterway (river, stream or drain) to pass under the road it is not a ford! It might well be a bridge=low_water_crossing as explained above -- or possibly a culvert if there is a single tube under the road under 3 meters in diameter. Culverts are tagged on the waterway which is split as bridges for only the part that crosses the road and tagged with tunnel=culvert and a layer=-1 tag.
In some areas, there are no formal paths, but several unpaved paths [example] very close to each other (within 100m) that all lead to the same destination or town. As of now, practice has been to add a way to the centermost or average of these paths. previous discussion]