Gravel road

The expected road traffic volume and the average daily truck passage must be considered during the design process as they will influence the thickness of this layer, along with the balances of gravel and fines.

Windrowing can be performed along the edges of roads in dry climates to allow easy access to gravel material for small repairs.

Crushed stone, also called road metal, is used because gravel with fractured faces will stay in place better than rounded river pebbles.

However laterite, called murram in East Africa, varies considerably in the proportion of stones (which are usually very small) to earth and sand.

Wheel motion shoves material to the outside (as well as in-between travelled lanes), leading to rutting, reduced water-runoff, and eventual road destruction if unchecked.

As long as the process is interrupted early enough, simple re-grading is sufficient, with material being pushed back into shape.

As an alternative method, humps can be formed in the gravel along the road to impede water flow, thereby reducing rutting.

Washboarding can also occur when graders exceed recommended speeds during the construction or maintenance phase causing the blade to bounce on the surface creating a pattern of widely-spaced corrugations.

[7] Corrugations from washboarding can become severe enough to cause vibration in vehicles so that bolts loosen or cracks form in components.

Proper grading is needed to remove the corrugations, and reconstruction with careful choice of good quality gravel can help prevent them reforming.

Dust control is routine practice on gravel roads in order to reduce the need for frequent maintenance, mitigate health concerns, and to prevent dust-related damage to roadside vegetation.

[4] Calcium chloride provides dust suppression through its hygroscopic properties, allowing moisture to be drawn in and retained by the compound.

Calcium chloride can be applied in either dry (pellet or flake) or wet (dissolved pre-prepared solution) form.

These roads are built mainly for the purposes of the logging industry and forest management workers, although in some cases they are also used for backcountry recreation access.

Typically, a high-clearance four-wheel drive vehicle is required to travel effectively on a road, especially where large potholes and/or waterbars are present.

They are commonly narrow, winding, and unpaved, but main haul roads can be widened, straightened or paved if traffic volume warrants it.