A New Approach to Indexing Localized Roughness of Pavement

This report presents the findings associated with the development of a new roughness index that is capable of quantifying localized pavement distresses such as are associated with pavement surface dips and bumps, concrete slab joint faulting, bridge-end bumps, potholes and so forth. Currently established pavement roughness indices, such as ride number (RN), profile index (PI) and international roughness index (IRI) are not able to effectively locate and rate such phenomenon due to inherent limitations. As such, a new pavement roughness index, herein to be termed the Localized Roughness Index (LRI), is promulgated. Development of the LRI was supported by preliminary field tests that were conducted and analyzed on bridge bumps so as to evaluate its effectiveness in indexing bump roughness. The LRI is derived using the accelerometer outputs which high-speed profilers provide, and it can effectively track the effects which vehicle travel speed and pavement surface characteristics have on ride quality. Based on the limited data collected through this research, vehicle travel can be considered comfortable if the LRI is smaller than 120,000 ft4/s8; uncomfortable if the LRI is between 120,000 and 600,000 ft4/s8; tolerable if smaller than 3,000,000 ft4/s8; and unsafe if greater than 15,000,000 ft4/s8. The LRI is a good supplement to IRI for locating and rating of localized roughness.