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5 CHAPTER 1 Introduction Background Because pavementtire noise is controlled primarily by (1) the tire design and materials and (2) roadway surface tex- It has long been recognized that the texture of portland ture and material properties, the highway community has been cement concrete (PCC) pavement surfaces directly influences actively engaged in evaluating the methods used to texture friction and safety characteristics (American Concrete Insti- pavements. Spurred on by the significantly lower noise of tute [ACI], 1988). Prior to 1967, most PCC surface textures asphalt concrete (AC) pavement surfaces when compared were constructed using a burlap drag process. However, at with transversely tined PCC surfaces, particular effort has been that time, this texturing method did not provide a minimum devoted to developing improved alternatives to the transverse frictional coefficient of 0.30, as was required by at least one tine texture. Among the earlier alternatives were (1) the longi- state--California (Neal, 1985). Consequently, other textur- tudinal tine that California specified starting in 1978 in spite ing methods were developed to improve frictional/safety of the requirement of FHWA guidelines for transverse tining characteristics, the most common of which is transverse tining (Neal et al., 1978; Hibbs & Larson, 1996); (2) the random (grooving the PCC surface perpendicular to the traffic direction (i.e., variable) transverse tine that was found to reduce or prior to curing). The uniform narrow grooves provide water eliminate the "whine" associated with uniform transverse drainage and increase the macro-texture of the surface, result- tining; and (3) the random (i.e., variable) skewed transverse ing in good wet-weather pavementtire friction and report- tine that was shown to eliminate whine and reduce overall edly a good safety record. noise (Kuemmel et al., 2000). As the volume of urban traffic increased steadily, vehicle Other methods of noise reduction for PCC pavements have noise emission became a concern (ACI, 1988). In 1973, the been evaluated internationally and more recently in the United Federal Highway Administration issued Policy and Procedure States. These include longitudinal diamond grinding, longitu- Memorandum 90-2, Noise Standards and Procedures that estab- dinal grooving, exposed aggregate concrete (EAC), porous lished noise criteria for federally funded highway projects PCC, shot-abraded PCC (e.g., Skidabrader), and ultra-thin (FHWA, 1973). From this time through 2004, over 2,205 mi proprietary surfacings (e.g., NovaChip and Italgrip System). (3,550 km) of noise barriers or combination berms and barri- Various strengths and weakness have been reported for all of the ers were built at a cost of over $2.7 billion (FHWA, 2006). The methods with regard to initial and long-term noise, friction, criteria have since been updated and are currently outlined in and other surface characteristics, as well as constructability and the Code of Federal Regulation (CFR) Title 23, Part 772, Proce- economics. Identifying optimal textures for various highway dures for Abatement of Highway Traffic Noise and Construction conditions and environments has been the goal in many of the Noise (U.S. Federal Government, 2008). past and ongoing investigations, and it is the goal in this study. While significant reductions in vehicle engine and drive- train noises were achieved in recent years, the noise associated Description of the Problem with pavementtire interaction has not been significantly reduced (Sandberg and Ejsmont, 2002). Public concern (espe- Tining generally is performed to enhance pavement-surface cially in urban areas) over the issue of high traffic noise and frictional characteristics and reduce potential for hydroplan- the substantial costs associated with noise emissions barriers ing, skidding, and wet-weather crashes. However, there is a have led to renewed interest in pavements that exhibit low- concern that the use of tining has evolved without adequate noise properties under traffic. consideration of the effects on noise generation, long-term