A New Approach to Measuring the Ride Quality of Highway Bridges

Report No: 02-R10

Published in 2002

About the report:

This report describes a field survey that applied modern high-speed profiling technology to examine the ride quality of bridge decks. The results of the survey were used to explore how various structural, service, and condition characteristics influence and sustain the ride quality of bridges. Survey data were also used to assess the use of the traditional 3-m (10-ft) straightedge in achieving good ride quality. This was accomplished by conducting a simulated rolling straightedge analysis for each bridge profile and comparing its outcome to an International Roughness Index (IRI) for each bridge. Although the IRI provides a popular basis for judging the ride quality of roadway pavements, a follow-up analysis revealed that designed-in girder camber can easily contribute as much as 1000 mm/km (64 in/mi) of roughness as indicated by the IRI. This finding discouraged the continued pursuit of using the IRI to assess bridge smoothness and prompted a renewed focus on the rolling straightedge simulation. The paper concludes with a demonstration of how this simulated 3-m straightedge can be used as a tool to discourage bridge deck roughness while taking advantage of modern inertial (and high-speed) road profiling equipment.

Disclaimer Statement:The contents of this report reflect the views of the author(s), who is responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Virginia Department of Transportation, the Commonwealth Transportation Board, or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. Any inclusion of manufacturer names, trade names, or trademarks is for identification purposes only and is not to be considered an endorsement.


  • Kevin K. McGhee, P.E.

Last updated: December 4, 2023

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