The forest service currently uses several aggregate surfacing design methods. Current design methods range from the "best-estimate" method to techniques that were developed or adapted by the differentforests or regions. These techniques have various deficiencies; thebest-estimate method has been criticized by the general accounting office. Also, several of these methods do not provide the technical capability to analyze unusual design situations, the effects of changes in the use of forest service roads, or the ability to incorporate technological advances. Such problems as different levels of failure criteria, seasonal haul traffic, variable tire pressures, and others have also not been met by the usda forest service "interim guidefor thickness design of flexible pavement structures". To meet these needs, the forest service recommended that a project be initiated to develop a second surfacing guide and computer program for the structural design of aggregate-surfaced and earth roads, utilizing existing technology as much as possible. This paper focuses on a description and evaluation of nine design methods that were deemed most suitable for use in forest service projects. The design methods evaluated include all of the known methods currently being used within the forest service. The other major organization performing aggregate-surfaced or earth design, the corps of engineers, is also represented.Recommendations are made pertaining to the need for field studies to refine the design algorithms for aggregate-surfaced and earth roads. This paper appears in transportation research record no. 1291, Fifth international conference on low-volume roads, may 19-23, 1991, raleigh, north carolina, volume 2.
Abstract