In this thesis, the relationship between the load carrying capacity and the transformed impact factor of the highway bridges were studied. The bridges are classified according to superstructures type. The result of the comparison between the load carrying capacity and the transformed impact factor, if the load capacity ratio of 0.57, the transformed impact factor was less in order of RC T-beam bridge, RC slab bridge, PC beam bridge, I-beam bridge. By the regression analysis on these results, the empirical formulae to predict the the load carrying capacity of bridge were suggested.