Sensitivity Analysis of the Cost Benefit Ratio as a Function of the Level of Service Targets in the Highway Maintenance Budget Allocation Process

The focus of this paper is the highway maintenance budget allocation decision-making process needed to achieve expected levels of service or performance targets. Establishing these performance targets must take into account the impact that such target levels can have on the financial resources required to achieve them. This paper reports on the sensitivity of the Cost/Benefit (C/B) ratio as a function of the pavement performance targets set by State DOTs. The C/B ratio is in itself a function of the yearly highway maintenance expenditures and the achieved Level of Service Index (LOSI). The LOSI has been modeled using three different functions, namely: step-wise, linear, and quadratic. The sensitivity of the C/B ratio to the performance targets is compared across the different functions used to model the LOSI. The model in this paper builds on the engine reported at the ASCE's International Workshop on Computing in Civil Engineering in 2007 and the findings augment those reported at the European Group's Intelligent Computing in Engineering Conference in 2008 where the sensitivity of the C/B ratio was shown as a function of the budget size. In addition, it builds on the findings reported at the TRB's Highway Economic Requirements Modeling and Data Integration Conference in 2008 where the sensitivity of the C/B ratio was shown as a function of the budget size, the budget profile, and the budget allocation strategy. The paper describes the results of six cases, namely; one step-wise, one linear and 4 quadratic. Our findings show that the best C/B ratios are achieved when quadratic functions are used to model the LOSI, which are fast in rewarding good performance.