Toward the development of an initial ride quality specification
State highway agencies in New England have recently adopted or are in the process of adopting performance specifications for new bituminous concrete pavements and overlays. These performance specifications cover issues such as asphalt content, in-place density, and initial ride quality. Associated with these specifications often are payment bonuses and penalties. Given the increasing trend to employ performance specifications, especially in initial ride quality, this dissertation focuses on the following questions. What are the factors that affect initial ride quality in new pavements and overlays, and what can be done to minimize the effects of those factors determined to be detrimental? What measurement devices, analytical methods, and measures are being employed to asses initial ride quality, and how suitable are these devices, analytical methods, and measures?
Currently, the trend in the New England region is to measure initial ride quality of new pavements and overlays with the International Roughness Index (IRI). Although implementation of the IRI is gaining acceptance in the industry, there is research that questions its use for this purpose.
Included in this dissertation are two field studies conducted in Massachusetts. The objective of these studies was twofold: (1) to focus on questions associated with paving operations and procedures, and their effect on roughness, and (2) to examine the suitability of an automatic road analyzer (ARAN) for the detection and measurement of initial roughness in new overlays.
Based on these two field studies, it was determined that paver stops during the placement of a bituminous concrete overlay produced roughness that was easily detectable and measurable by a skilled inspector. It was also determined that the while the ARAN was capable of accurate and precise measurements of overall initial ride quality, it was not sufficiently sensitive to determine the exact location of this roughness caused by paver stops. For this reason, it was determined that the ARAN be used in conjunction with other measurement techniques.