Abstract
The current state-of-the-practice for pavement design only accounts for traffic load application
without considering the speed and highway geometry as design criterion. This paper investigates the
effect of geometric design elements including horizontal curves, vertical gradients and U-turns on
pavement performance at different traffic characteristics and pavement structures. The effects of
theses parameters on Pavement Condition Index (PCI) and International Roughness Index (IRI) were
investigated using simple, multiple, and stepwise linear regression to develop prediction models for
special geometric sections. In this study, field data were collected for surface pavement distresses, for
sections with special geometric features, varied traffic characteristics, and different pavement
structures. Comparison between the pavement conditions of sections with special geometric features
and those of their reference straight road sections was performed. The results showed significant
difference between PCI of special geometric sections and their reference sections. So, the geometry
factor needs to be considered in structural design of pavements. This paper also showed that speed is
one of the most important factors influencing pavement deterioration especially at upgrade sections
and horizontal curves. Prediction models were built to forecast the pavement conditions for sections
with vertical gradients and horizontal curves.