The Lithuanian state road network consists of more than 21,000 km of roads, and gravel roads dominate (43.3%). While the 1998-2000 Paving of Gravel Roads Program was being implemented, there were a few issues in estimating investments that could determine the implementation alternatives of the rehabilitation project. Total costs of renovated gravel roads depended on the climate and geological and hydrological conditions of a location as well as traffic and gravel road characteristics. Roads, like engineering buildings, have to be of sufficient strength and durability, and they should correspond to traffic volume. The results of tests showed diversity of pavements and the characteristics of renovated gravel roads. Gravel roads vary by road width, pavement structure, pavement materials, and traffic. In analyzing traffic on gravel roads, the roads were classified into four groups according to traffic volume. Frequently, the strength of subgrade soils determines the structure of renovated gravel roads. The authors carried out tests on road subgrades under different geomorphologic and geological conditions, estimating the structure, physical conditions, and mechanical properties of these subgrades. According to the test results the strength of existing gravel roads depends on the strength of the subgrade, the thickness of the gravel road, and the quality of the gravel. The equivalent deformation modulus of the gravel roads is described by a binomial. In selecting structures for reconstruction of gravel roads, mathematical models are suggested.