Investigating the Sensitivity of Optimal Network Safety Needs to Key Safety Management Inputs

This paper uses optimization methodologies and project-level cost and effectiveness data to assess long-term safety needs for a network. The optimal solution specifies values of decision variables (locations, years, and safety improvement types) such that overall cost-effectiveness at the network level is maximized under budgetary constraints. The paper evaluates the impact of alternative levels of safety funding on systemwide crash reduction and investigates the sensitivity of optimal funding levels to key safety management inputs. To demonstrate the methodology, data from Indiana's state highway system are used. It is shown that increases in overall safety funding have an increasing effect on crash reduction, but such increasing benefit tapers off after a certain point. It was determined that over a 10–year period (2005 to 2015) the optimal annual average safety need for the network is approximately $450 per mile. Furthermore, it is shown that the overall network safety funding need is sensitive to the method for identifying hazardous locations and the criterion for economic evaluation. The results show that with currently available data it is possible for highway agencies to incorporate road safety proactively into their transportation planning processes in a comprehensive and systemwide context. Also, agencies can use the methodology to determine optimal safety funding levels on their networks for possible comparison with current levels.