A dirt road or track is a type of unpaved road not paved with asphalt, concrete, brick, or stone; made from the native material of the land surface through which it passes, known to highway engineers as subgrade material. Dirt roads are suitable for vehicles; a narrower path for pedestrians, animals, and possibly small vehicles would be called a dirt track—the distinction is not well-defined. Unpaved roads with a harder surface made by the addition of material such as

gravel Gravel is a loose aggregation of rock fragments. Gravel occurs naturally throughout the world as a result of sedimentary and erosive geologic processes; it is also produced in large quantities commercially as crushed stone. Gravel is classifi ...

and

aggregate Aggregate or aggregates may refer to: Computing and mathematics * collection of objects that are bound together by a root entity, otherwise known as an aggregate root. The aggregate root guarantees the consistency of changes being made within the ...

(stones), might be referred to as dirt roads in common usage but are distinguished as improved roads by highway engineers. (Improved unpaved roads include gravel roads, laterite roads, murram roads and

macadam Macadam is a type of road construction, pioneered by Scottish engineer John Loudon McAdam around 1820, in which crushed stone is placed in shallow, convex layers and compacted thoroughly. A binding layer of stone dust (crushed stone from the o ...

ized roads.) Compared to a gravel road, a dirt road is not usually graded regularly to produce an enhanced camber to encourage rainwater to drain off the road, and drainage ditches at the sides may be absent. They are unlikely to have

embankment Embankment may refer to: Geology and geography * A levee, an artificial bank raised above the immediately surrounding land to redirect or prevent flooding by a river, lake or sea * Embankment (earthworks), a raised bank to carry a road, railwa ...

s through low-lying areas. This leads to greater waterlogging and erosion, and after heavy rain the road may be impassable even to off-road vehicles. For this reason, in some countries, such as

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

and New Zealand and Finland, they are known as ''dry-weather roads''. Saviselkä 2

Dirt roads take on different characteristics according to the soils and geology where they pass, and may be sandy, stony, rocky or have a bare earth surface, which could be extremely muddy and slippery when wet, and baked hard when dry. They are likely to become impassable after rain. They are common in rural areas of many countries, often very narrow and infrequently used, and are also found in

metropolitan area A metropolitan area or metro is a region that consists of a densely populated urban agglomeration and its surrounding territories sharing industries, commercial areas, transport network, infrastructures and housing. A metro area usually com ...

s of many developing countries, where they may also be used as major highways and have considerable width. Terms similar to dirt road are ''dry-weather road'', ''earth road'', or the "Class Four Highway" designation used in the People's Republic of China. A ''track'', ''dirt track'', or ''earth track'' would normally be similar but less suitable for larger vehicles. Dirt roads almost always form a washboard-like surface with ridges. The reason for this is that dirt roads have tiny irregularities; a wheel hitting a bump pushes it forward, making it bigger, while a wheel pushing over a bump pushes dirt into the next bump. However, the surface can remain flat for velocities less than 5 mph.

Driving on dirt roads

While most gravel roads are all-weather roads and can be used by ordinary

car A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods. The year 1886 is regarded as ...

s, dirt roads may only be passable by trucks or four-wheel drive vehicles, especially in wet weather, or on rocky or very sandy sections. It is as easy to become bogged in sand as it is in mud; a high clearance under the vehicle may be required for rocky sections. Driving on dirt roads requires great attention to variations in the surface and it is easier to lose control than on a gravel road. DirtRoadByAmiltonReis

Laterite and murram roads

In Africa, parts of Asia, and parts of

the Americas The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North America, North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World. ...

laterite Laterite is both a soil and a rock type rich in iron and aluminium and is commonly considered to have formed in hot and wet tropical areas. Nearly all laterites are of rusty-red coloration, because of high iron oxide content. They develop by ...

soils are used to build dirt roads. However, laterite (called ''murram'' in

East Africa East Africa, Eastern Africa, or East of Africa, is the eastern subregion of the African continent. In the United Nations Statistics Division scheme of geographic regions, 10-11-(16*) territories make up Eastern Africa: Due to the historical ...

), varies considerably. It ranges from a hard

to a softer earth embedded with small stones. Not all laterite and murram roads are therefore strictly gravel roads. Laterite and murram which contains a significant proportion of clay becomes very slippery when wet, and in the rainy season, it may be difficult even for four-wheel drive vehicles to avoid slipping off very cambered roads into the drainage ditches at the side of the road. As it dries out, such laterite can become very hard, like

sun-dried brick A mudbrick or mud-brick is an air-dried brick, made of a mixture of loam, mud, sand and water mixed with a binding material such as rice husks or straw. Mudbricks are known from 9000 BCE, though since 4000 BCE, bricks have also bee ...

Image gallery

File:Dirt Road - Fremont - CA.jpg, Dirt road in

Fremont, California Fremont is a city in Alameda County, California, United States. Located in the East Bay region of the San Francisco Bay Area, Bay Area, Fremont has a population of 230,504 as of 2020, making it the fourth List of cities and towns in the San Fra ...

File:655 Wrightwood Avenue Circa 1880, Lincoln Park Chicago Illinois.jpg, Wrightwood Street in

Lincoln Park neighborhood Lincoln Park is a designated community area on the North Side of Chicago, Illinois. Lying to the west of Lincoln Park, Chicago's largest park, it is one of the most affluent neighborhoods in Chicago. History In 1824, the United States ...

of Chicago, Illinois, circa 1880 File:Frühlingslandschft Aaretal Schweiz.jpg, Mountain track in Switzerland File:DryDirtRoadDetail.jpg, Detail of a dry, loamy road File:Bike on the rough roads in Bagamoyo.jpg, Cycling on a rough road in Tanzania File:Le transport au Bénin 01.webm, Spraying dirt road with water in Benin

Driving on dirt roads

Laterite and murram roads

Image gallery

References

See also