About two-thirds of the highways in the United States and 90% of all roads worldwide are unsurfaced or lightly surfaced low-volume roads. Many systems are being used to manage the maintenance of these roads. In this manual we describe a method that can help local highway agencies manage their unsurfaced roads. The result of the system is a rating for each section of road indicating how badly that section needs repairs. If you are managing unsurfaced roads, this system will help you keep your road system in good shape by identifying problem areas. Neglected problem areas can deteriorate quickly and require costly major repairs. The ratings from this system will help you decide how to divide up your maintenance budget so that you can get more for your money. An unsurfaced road is any road that does not have portland cement concrete, asphalt concrete or any other surface treatment. Some agencies consider gravel to be a surfacing material; for the purpose of this manual a gravel road in an unsurfaced road.

A method for rating the surface drainage and conditions of unpaved roads has been developed, and a field manual has been prepared to assist county, municipal, military and township highway agencies in managing the maintenance of such roads. The types of distress found in unpaved roads are categorized and listed in the manual. For each type of distress listed, there is a description of the distress and the levels of severity, an illustration, and a measurement method. The manual also includes instructions on how to inspect unsurfaced road conditions, a field inspection work sheet, and a family of deduct value curves for the distress types and associated severity levels. The curves were validated using data gathered during seven field surveys throughout the United States. This report describes the development of the deduct value curves for the seven distresses identified in unsurfaced road maintenance. The development of the original curves and the adjustments after each field trip are described. The surface and drainage rating method and maintenance strategies can be used alone, or they can be adapted for use with any existing computerized pavement management system (PMS). The rating method and strategies are compatible with the PAVER PMS developed by the U.S. Army Corps of Engineers and the American Public Works Association. With appropriate software modifications, an unsurfaced roads component of the PAVER PMS will be available for use, giving local highway agencies a more comprehensive roadway management system. (SDW).