Estimating International Roughness Index from Pavement Distresses to Calculate Vehicle Operating Costs for the San Francisco Bay Area

Incorporating models that estimate road user costs and user benefits or both from different management strategies would increase the road network asset management system capabilities. Vehicle operating cost (VOC) can be a major part of road user costs, and pavement surface roughness is a major factor that affects VOC. This study was based on an effort to establish a correlation between pavement roughness and pavement distresses for asphalt concrete surface with the objective that the developed roughness model could be utilized to estimate VOCs for the streets in the cities and counties of the San Francisco Bay Area directly from pavement distresses. Due to the lack of roughness data for Bay Area city streets, Strategic Highway Research Program distress data for California Long-Term Pavement Performance sites were used as an initial effort to establish the model. A systematic approach was used to come up with a reasonable correlation between international roughness index (IRI) and pavement condition. The current roughness model can be used to estimate surface roughness if the pavement surface distress data are available. This model could be included, along with an additional incorporation of established relations between VOC and IRI, in the Bay Area agencies' pavement management system, to estimate VOC directly from pavement distresses. Finally, some recommendations are provided to the agencies in the Bay Area cities and counties on how to utilize the model and how to refine the initially established model in the future.