Best Practices for Achieving and Measuring Pavement Smoothness, A Synthesis of State-of-Practice

Pavement smoothness specifications have evolved significantly over the past decade. More and more states are moving away from profilograph-based smoothness specifications to International Roughness Index (IRI)-based specifications. Unfortunately, a limited history with the usage of IRI-based specifications has led to some confusion over how best to structure a specification in terms of test methods and profiling equipment, thresholds for full pay/incentive/disincentive, and requirements for localized roughness or “must correct” areas. This limited history has also led to contractors who were used to profilograph-based specifications struggling to achieve the same level of quality under IRI-based specifications. This synthesis summarizes the current state-of-the-practice for IRI-based pavement smoothness specifications in the U.S. It highlights recent and current research related to pavement smoothness and provides general best practices for construction to help achieve requirements for IRI-based specifications.