U.S. Department of Transportation
Federal Highway Administration
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Washington, DC 20590

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Bridges & Structures

Construction Unit Costs Development Criteria

  1. A construction unit cost is provided by the States for new or replaced highway bridges constructed with Federal funds on Federal-aid highways (highway bridges on the NHS and other Federal-aid highways) and on non Federal-aid highways (highway bridges on local roads and rural minor collectors; off-system highway bridges). The total cost of eligible items used to construct all bridges is divided by the total area of all bridges to determine the average unit cost by system.
  2. All new or replaced highway bridges let or awarded during the appropriate fiscal year are used.
  3. Culverts are excluded (multiple cell box culverts, long span culverts and multiple pipe installations) from the calculations.
  4. The total deck area of the new or replaced bridge is used for all calculations. The length dimension is as described for Item 49 from the National Bridge Inventory (NBI) and the width dimension is to be as described for NBI Item 52 in the Recording and Coding Guide for the Structure Inventory and Appraisal of the Nation's Bridges.
  5. Bridges involving unusual circumstances or types of construction not routinely used by the State that significantly raise or lower the unit cost are not included. Generally, certain types of bridges can be identified as unusual - movable, cable-stayed, suspension, segmental and other structures that have a clear unsupported length greater than 500 feet. However, certain States that have built numerous types of unusual bridges, e.g. segmental bridges, may no longer consider such bridges as unusual. Therefore, the States are given some discretion in making the determination concerning the definition of unusual. Unusual circumstances may include extremely difficult access conditions and the occurrence of extreme events during construction.
  6. Bridges that are under stage construction are not included unless the final stage has been bid and a total unit cost can be obtained. If a bridge is included in a design build or lump sum contract, only eligible costs are included in the unit cost calculations. If this cannot be accomplished, the State may use the previous year's unit cost for these bridges.
  7. Unit costs are based on bridge costs only. A list of specific items not included is provided below. The list is not all-inclusive.

Cost Items not used in the Unit Cost Calculations

  • Mobilization
  • Demolition of Existing Bridges
  • Approach Slabs (approach slabs may be included when paid for as bridge item, e.g. on integral abutment bridge).
  • Stream Channel Work
  • Riprap
  • Slope Paving
  • Earthwork (exclusive of structural excavation, structural backfill, and earthwork associated with Geosynthetic Reinforced Soil Integrated Bridge Systems)
  • Clearing and Grubbing
  • Retaining Walls not attached to the Abutment
  • Guardrail Transitions to Bridges
  • Maintenance and Protection of Traffic
  • Detour Costs
  • Signing and Marking
  • Lighting
  • Electrical Conduit
  • Inlet Frames and Grates
  • Field Office
  • Construction Engineering Items
  • Training
  • Right-of-Way
  • Utility Relocation
  • Contingencies
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Updated: 06/27/2017
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000