Dirt road

Terminology

Similar terms

Terms similar to dirt road are dry-weather road, earth road, or the "Class Four Highway" designation used in China. A track, dirt track, or earth track would normally be similar but less suitable for larger vehicles—the distinction is not well-defined. Laterite and murram roads, depending on material used, may be dirt roads or improved roads.

Improved road

Unpaved roads with a harder surface made by the addition of material such as gravel and aggregate (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 and macadamized roads.

Characteristics

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 embankments 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 and New Zealand and Finland, they are known as dry-weather roads.

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 areas of many developing countries, where they may also be used as major highways and have considerable width.

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.

Image gallery

File:Dirt Road - Fremont - CA.jpg|Dirt road in Fremont, California File:655 Wrightwood Avenue Circa 1880, Lincoln Park Chicago Illinois.jpg|Wrightwood Street in Lincoln Park neighborhood of Chicago, Illinois, 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 File:Bowerman Road Kingsley MI.jpg|Rural dirt road near Kingsley, Michigan File:DirtRoadByAmiltonReis.jpg|Dirt road in Brazil File:2025-05-11 Rocky road between Kiketi and Kojori.jpg|A road passing through a rocky outcrop in Tbilisi

References

References

1. (2016-04-18). "Minicars, Maglevs, and Mopeds: Modern Modes of Transportation Around the World: Modern Modes of Transportation around the World". ABC-CLIO.
2. (2007-08-15). "Road Bumps: Why dirt roads develop a washboard surface".