Several defects may appear in unpaved roads under cyclic loading. From engineering point of view ruts are the most important defects. The behavior of unpaved road under repetitive loads with a geogrid on a sand subgrade was investigated through a laboratory testing program. Twenty two large scale laboratory model tests under the effect of cyclic loading were conducted on road section. Parameters investigated in the testing program include base layer thickness, aperture size of the grids, subgrade degree of compaction, and geogrid location. The experimental results indicated that the inclusion of geogrid sheet placed at the interface reduced the rut depth by 16% to 31% depending on the base course thickness. The most advantageous location of one geogrid layer was in the top quarter of the base course layer.  The results show that in all cases of cyclic loading in the laboratory model tests, the use of geogrid improved the bearing capacity and reduced the rut depth in comparison with the unreinforced case.