The purpose of the Bridge Development Report is to select the most cost efficient and appropriate structure type for the site under consideration. This chapter describes a three-step process to estimate bridge costs based on FDOT historical bid data. The first step is to utilize the average unit material costs to develop an estimate based on the completed preliminary design. The second step is to adjust the total bridge cost for the unique site conditions by use of the site adjustment factors. The third and final step is to review the computed total bridge cost on a cost per square foot basis and compare this cost against the historical cost range for similar structure types. This process should produce a reasonably accurate cost estimate. However, if a site has a set of odd circumstances, which will affect the bridge cost, account for these unique site conditions in the estimate. If the estimated cost is outside the cost range in step three, provide documentation supporting the variance in cost.
The three-step process described in this chapter is not suitable for cost estimating structure types without repeatable bid history. Estimates for unique structures such as movable, cable stayed, cast-in-place on form travelers, arches and tunnels should based on construction time, labor, materials, and equipment.