10.3.6 Cost-Benefit Analysis

A cost-benefit analysis should be done for each alternative to gain a complete picture of benefits and cost, particularly to achieve maximum crash reduction benefits. For this purpose, the SII spreadsheet can be used. In its most basic form, the SII is the ratio of the annual savings in preventable crash costs that have occurred at a location to the cost of constructing the proposed improvement. Costs include cost of constructing or implementing improvements and cost of maintenance. Benefits are calculated in crash reduction savings, to weigh each cost in relation to its importance to the overall project purpose when comparing alternatives. A cost-benefit analysis consists of three parts:
  1. Opinion of Probable Construction Cost (OPCC)
    • Estimate overall construction cost for the improvements.
    • Review similar completed projects for an approximation.
    • Include costs for ROW acquisition, utility relocations, and environmental impacts due to construction.
  2. Life Cycle Cost
    • Compares intersection control costs including construction, maintenance, and operational costs.
    • NCHRP’s Life-Cycle Cost Estimation Tool:
      • For cost parameters, use TxDOT’s Road User Costs and NSC’s PCE average economic costs per injury severity.
  3. Safety Improvement Index (SII)
    • TxDOT’s SII Calculator
      • Refer to TxDOT’s HSIP Guidelines for CRF, service life, and preventable crash information for countermeasures permitted in the HSIP. Internal TxDOT personnel use the MicroStrategy SII reports, and external partners use the SII calculator worksheet.