Another problem with gravel roads is washboarding — the formation of corrugations across the surface at right angles to the direction of travel. Narrow-spaced washboarding can develop on gravel roads due to inconsistent moisture levels in the gravel, poor quality gravel, and vehicular stress to the road. 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. 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. Additionally, installing a cellular confinement system will prevent the washboard-like corrugations from occurring.