Abstract: Pavements life will be increased by timely maintenance and the expenses will be decreased effectively by choosing the optimum time for repairing and preventive maintenance, usually, pavement life parameter is used as an optimum time for repairing. The cracks dimensions, as a measurable parameter in pavement level, can also help us choosing the repairing and preventive maintenance time. In this research, the procedure expense of preventive maintenance and repairing is considered as a measure of choosing tine for sealing cracks. If it is not possible to seal the cracks, this expenses should be equal wilt the expanses of operating and repairing the pavement using the relations of the cracks progression and calculated expenses of maintenance and repairing operations unit in pavement unit, a relation has been proposed for determining the cracks dimensions to be soiled.