Gravel is a very useful, inexpensive material that does many wonderful things for humankind. Gravel may be defined as many small stones lying on the earth. Gravels, technically, are water-worn stones that are rounded and may be an inch in size or less.
Crushed stone is often called gravel, but is much more angular and not necessarily water worn. Larger crushed stone is called ballast. Gravel may contain fines (as small as sand) or it may be delivered washed (no sand). Crush-and-run is the term for crushed stone that contains about 4% fines by weight. Crush-and-run is best for surfacing a driveway with crushed rock. Washed stone stays loose and never packs.
Ballast is used effectively to support railroad rails. The rails can be adjusted to very precise elevations, resulting in a very smooth roadbed. Crushed stone can also effectively result in smooth walkways and roadways. When proper design is implemented, crushed stone access ways are very desirable and inexpensive.
The primary bane of gravel roads is water on the steep parts usually from weather. Gravel roads need to experience a minimum of water from rain and flood. A road designed to shed water will remain in good condition indefinitely. When water is allowed to run along a gravel road, there is a maximum potential for damage from washouts. The roadway should be graded to cause water to flow across and off the road. Water should always flow off a gravel roadway at an angle of 90 to 135 degrees, that is, across the road. Water flowing at an angle of 180 degrees (along the roadway) is the worst angle. This water causes increasing damage all along the roadway.
Gravel roads are easier to damage when they are steep. There is a limit to the steepness that should be allowed for a gravel road. Flowing water is a special problem in these areas. Also, vehicles cause movement of gravels due to braking and wheel spinning action. The steeper gravel roads cannot shed the water sideways effectively.
Gravel roads are also susceptible to flat spots. Where ever there is a flat spot, a water puddle can form. An unthinking driver drives through the middle of the water puddle. Loose gravel and sand splashes out of the puddle, thus creating a pothole.
Drivers can drive on gravel roadways in ways that help maintain the roadway. Never drive in the ruts of a gravel road. Never drive directly through a pothole. Always drive on the lower edge of loose gravel deposits, potholes and ruts. This will help to allow the water to run off the roadway.
In summary, gravel roads always need to have a slight slope directly to the side of the road.