This paper estimates the elasticities of highway stock and maintenance spending by the growth accounting method. In addition, the continuous effects of highway stock and maintenance spending were examined. Highway stock has a positive, substantially large, and continuous effect on the privateproductivity, while maintenance spending, as a factor enhancing the effectiveness of highway stock, has an insignificant and negligibly small positive effect. Therefore, the productivity boost effect from road service comes mainly from the amount of highway stock rather than the effectiveness through maintenance spending.