To the major function as a structural portion of the pavement, subbase courses may have additional secondary functions, such as: (i) Preventing the intrusion of fine-grained roadbed soils into base courses–relatively densegraded materials must be specified if the subbase is intended to serve this purpose. (ii) Minimize the damaging effects of forst actionmaterials not susceptible to detrimental frost action must be specified if the subbase is intended for this purpose. (iii)Preventing the accumulation of free water within or below the pavement structure-a relatively free-draining material may be specified for the subbase if this is the intention. (iv)Providing a working platform for construction equipment-important when roadbed soil cannot provide the necessary support.