Potential Bias of Response Type Road Roughness Measuring Systems: Causes and Remedial Measures

Response-type road roughness measuring systems estimate pavement roughness from correlation equations. Most of these systems recommend to maintain a constant survey speed or to keep the speed within a certain range. But carrying out a survey with this speed constraint may not always be possible due to the existence of traffic control devices and heavy traffic flow. Therefore, these systems may produce a significant bias in roughness measurement because of survey speed fluctuations. The objective of this study is to develop calibration equations that eliminate the bias produced by survey speed fluctuations. A simplified regression relationship for IRI with bump integrator reading and survey speed as explanatory variables is developed using ROMDAS bump integrator. Using a case study, this study also investigates how the bias created by speed fluctuations affects roughness and demonstrates how developed calibration equations eliminate that bias.