This manual presents the Roads EconomicDecision Model (RED) developed to improve thedecision-making process for the development and maintenanceof low-volume rural roads. The model performs an economicevaluation of road investments options using the consumersurplus approach and is customized to the characteristicsand needs of low-volume roads such as the high uncertaintyof the assessment of the model inputs, particularly thetraffic and condition of unpaved roads, the importance ofvehicle speeds for model validation, the need for acomprehensive analysis of generated and induced traffic, andthe need to clearly define all accrued benefits. REDcomputes benefits for normal, generated, induced, anddiverted traffic, and takes into account changes in roadlength, condition, geometry, type, accidents, and days peryear when the passage of vehicles is further disrupted by ahighly deteriorated road condition (wet season). Users canadd to the analysis other benefits, such as non-motorizedtraffic, social services and environmental impacts, ifcomputed separately. The model is presented on a series ofExcel 2000 workbooks that collect all user inputs, presentthe results on an efficient manner and performs sensitivity,switching values and risk analyses.