The Arizona Department of Transportation (ADOT) implemented an incentive/disincentive asphalt concrete (AC) smoothness specification in 1990. Since then hundreds of projects have been tested for smoothness. These projects have included a wide variety of layer combinations of one or more of the following: overlay, remove, replace, and finishing course. The number of projects and variation in design allows comparisons of the smoothness results for different design strategies as well as trends in smoothness results over time. In addition to the tests on the final surface, many projects were also tested on intermediate lift surfaces.

This publication contains papers presented at a December 2001 symposium, focusing on hot mix asphalt (HMA) smoothness measurements, specifications, and equipment. Five papers provide insight into the development and implementation of roughness specifications for pavements, and two papers offer natio

Smoothness, the absence of bumps and dips in the riding surface of a pavement, improves the quality of the ride and is believed to prolong the life of the pavement. This research addressed the impact of potential pay adjustments for smoothness on maintenance contract prices for hot-mix asphalt. In addition to the construction costs associated with potential incentives/disincentives for smoothness, the research examined the financial value of the resulting product (presumably smoother pavements). The analysis included maintenance cost savings for the owner/agency, as well as any reduction in delay and operating costs for the motoring public. A detailed statistical analysis of 5 years of Virginia's plant mix resurfacing schedules found no statistically definitive impact on bid price as a result of the Virginia Department of Transportation's (VDOT) special provision for rideability for asphalt pavements. A similar analysis on a more focused data set, however, did document a lifetime reduction in the International Roughness Index (IRI) of almost 9 in/mi. This reduction in roughness (increase in smoothness) implies an increase in pavement service life, which translates into reduced annual maintenance costs. Although the analysis supports as much as 7 years in additional functional life, an example calculation demonstrates that just a 2-year life extension will supply approximately $1,295 (about 6% of material costs) in owner/agency savings for every lane-mile of highway that is resurfaced under the special provision for rideability. If VDOT continues to employ the special provision with the frequency it has averaged over the past 4 years (1,033 lane-miles per year), using the special provision will save on the order of $1.3 million per year. The lifetime decrease in roughness can lead to even more dramatic user cost savings. One real example provided in the report demonstrates a fuel cost savings (for trucks alone) of $160,000 over a 10-year period for each lane mile of highway that is resurfaced under the special provision for rideability.

Design related project level pavement management - Economic evaluation of alternative pavement design strategies - Reliability / - Pavement design procedures for new construction or reconstruction : Design requirements - Highway pavement structural design - Low-volume road design / - Pavement design procedures for rehabilitation of existing pavements : Rehabilitation concepts - Guides for field data collection - Rehabilitation methods other than overlay - Rehabilitation methods with overlays / - Mechanistic-empirical design procedures.

This report contains guidelines and recommendations for managing and designing for friction on highway pavements. The contents of this report will be of interest to highway materials, construction, pavement management, safety, design, and research engineers, as well as others concerned with the friction and related surface characteristics of highway pavements.

TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 338: Thin and Ultra-Thin Whitetopping summarizes available information to document how state departments of transportation and others are currently using thin and ultra-thin whitetopping overlays among various pavement rehabilitation alternatives. The report covers all stages of the proper application of whitetopping overlays, including project selection, design, materials selection, construction, maintenance, and eventual rehabilitation or replacement.