Use of Distress and Ride Quality Data to Determine Roughness Thresholds for Smoothing Pavements as a Preventive Maintenance Action

In this discussion, 462 pavement sections from 37 projects in Michigan were analyzed to investigate the interaction between pavement surface roughness and distress. The main hypothesis of this research is that an increase in roughness leads to higher dynamic axle loads, which in turn can lead to a tangible acceleration in pavement distress. If this relationship is established, then it will be possible to plan a preventive maintenance (PM) action to smooth the pavement surface. Such a PM action is bound to extend the service life of the pavement by several years. The objective of the research presented was to develop such roughness thresholds. The selected projects include 13 rigid, 15 flexible, and 9 composite pavements. The ride quality index (RQI) and distress index were used as measures of surface roughness and distress, respectively. To get a good relationship between distress caused by dynamic loading and surface roughness, dynamic-load-related distress types were extracted. The analysis showed very good relationships between distress and roughness for rigid and composite pavements ( R 2 = 0.739 and 0.624). However, for flexible pavements there was significant scatter ( R 2 = 0.375), reflecting the higher variability in flexible pavement distresses. A logistic function was used to fit the data, and roughness thresholds were determined as the RQI-values corresponding to peak acceleration in distress. These were determined to be 64 [international roughness index (IRI) = 1.99 m/km or 124 in./mi] for rigid pavements and 51 (IRI = 1.43 m/km or 89 in./mi) for composite pavements.