A pavement design method is described for low-volume roads in the cold and snowy regions of Japan. The replacement thickness required to prevent frost heave is greater than the thickness necessary to bear heavy vehicles. Pavement costs are higher in cold regions than in the milder regions of southern Japan. Cost-effective pavement structures are proposed for low-volume roads under the traffic classifications and weather conditions of the cold and snowy regions. Special attention is paid to pavement design and antifrost replacement thickness. Pavement thickness is determined by the number of 5-ton (50-kN) equivalent wheel loads in one direction that are expected during the design period and the design CBR of the subgrade. The lowest of five traffic volume classifications, L, specifies a total of 30,000 passes by 5-ton (50-kN) equivalent wheel loads in one direction. The pavement structure for the L classification, which applies to low-volume roads with few heavy vehicles, is overestimated. There are four classifications for low-volume roads with recommended pavement structures. Weather conditions and traffic volume are very important factors in the pavement design of low-volume roads that are covered with packed snow. The depth of frost penetration on these roads is less than that of bare pavements because of the insulating effect of the snow layer. Therefore, because the insulating effect of snow can be expected, the thickness of the antifrost layer can be reduced when the pavement is replaced. In order to practically apply this design procedure, the following work must be performed. The earliest date at which snow continuously covers the pavement must be estimated,. the freezing index of the earliest date and the total freezing index must be determined from meteorological records of the, project area, and the thermal constants of the packed snow· layer and pavement materials must be calculated. It was found that more costeff ective pavement designs of low-volume roads are possible in cold and snowy regions when the ins. ulating effects of the packed-snow layer are considered.

The total length of roads in Japan is nearly Ij 20 000 km, over 80 percent of which are s~ condary roads, including low-volume roads. Trunk roads are nearly 100 percent paved, and maintenance and improvement are important problems. Low-cost paving methods must be developed to extend the life of lowvolume roads that are paved.