STC Publication: “Best Practices for Achieving and Measuring Pavement Smoothness, A Synthesis of State-of-Practice”

The Louisiana Transportation Research Center (LTRC), USA and the Southeast Transportation Consortium (STC) released a publication titled “Best Practices for Achieving and Measuring Pavement Smoothness, A Synthesis of State-of-Practice”, summarizing current US concrete and asphalt pavement smoothness requirements. The report provides timely information as the US undergoes a major shift in the way smoothness specifications are written. A growing number of states are moving away from profilograph-based (device used to measure pavement surface roughness) smoothness specifications in favor of specifications based on a more widely-accepted and precise measure of pavement smoothness: the International Roughness Index (IRI). Forty six (46%) of concrete pavement specifications and seventy eight percent (78%) of US state asphalt pavement specifications are currently based on IRI. As more states move toward IRI-based specifications, these numbers are expected to continue growing. LTRC’s report will help contractors, agencies, and engineers adjust to the change.

Agencies are switching to IRI in order to more accurately assess the smoothness of their roads. IRI is reproducible and comparable across the world. However, limited knowledge of IRI can cause confusion during specification development or pavement construction. IRI is calculated using a mathematical model to provide a “true profile” of the pavement’s actual cross section—it is a clearer picture of the road’s smoothness.

LTRC’s report, written by the pavement engineering firm The Transtec Group, summarizes the state-of-practice for US state DOT pavement smoothness specifications based on IRI. The authors provide a summary of best construction practices for achieving:

• Required pavement smoothness
• Current smoothness specifications
• IRI collection and processing technology
• Construction acceptance
• Current research
• Educational and training practices

Smooth pavements provide significant benefits to the public and agencies. Smoother pavements can lead to increased public
satisfaction with the road system, a reduction in fuel consumption, and longer-lasting pavements. US state departments of transportation (DOTs) prescribe certain levels of smoothness in pavement specifications and often penalize or provide bonuses to contractors depending on the smoothness they provide. This synthesis summarizes the current state-of-the-practice for IRI-based pavement smoothness specifications in the US. It highlights recent and current research related the pavement smoothness, and provides general best practices for construction to help achieve requirements for IRI-based specifications.

To read the full report in PDF form, please click here.

To request further information, contact The Transtec Group at www.TheTranstecGroup.com.