Despite the expense of construction and maintenance, forest roads are still essential to provide land accessibility and management. Quality of roads depends largely on the pavement conditions. The heavy machines directly induce stress on pavement as first layer of a road.  The current study aims at investigating the equivalent axle load, the devastation wrought by the axis to the devastation wrought by the standard axis (8.16 tons), on pavement deterioration. To develop the equivalent axle load model, 50 km of forest roads, under management of Wood and Paper Company, was selected with respect to the trucks and cars and critical values and growth rates of pavement failures were identified using the log of changes failure to the equivalent axial load. The results showed that highest proportion of failure involves trucks 15 tons (growth rate 10.2), nine-ton trucks, Nissan truck and cars with the values of 5.77, 1.8, 0.64 and 0.45 respectively. According to the obtained results, less equivalent axle load vehicles with lower the volume of timber and wood out of the forest with enough time should be utilized.