This report is a joint study prepared for the Sacramento County Public Works Agency, Transportation Division by the Sacramento County Department of Environmental Review and Assessment and Bollard and Brennan, Inc., consultants in acoustics and noise control engineering. The purpose of this report is to document the effectiveness of rubberized asphalt as a traffic noise mitigation measure. Rubberized asphalt is a bituminous mix, consisting of blended aggregates, recycled rubber and binding agents. The rubber is often obtained from used tires. Studies conducted locally, nationally, and internationally, have shown that rubberized asphalt can reduce the noise pollution that is associated with roadway traffic. The specific findings of this analysis are based primarily on a series of traffic noise level measurements conducted along the Alta Arden Expressway, between Howe and Watt Avenues, from 1993 to the present. Although similar noise measurements have been conducted along a segment of Antelope Road, the smaller number of variables affecting the measured traffic noise levels along the Alta Arden Expressway before and after paving with rubberized asphalt made that roadway a more statistically reliable test subject. Therefore, this analysis focuses on the series of test results for Alta Arden Expressway. Bond Road between Stockton Boulevard and Florin Road, was used as the control site for conventional (non-rubberized) paving. Although the Bond Road test segment was widened at the time of paving with conventional asphalt, the relationship of the roadway to the noise measurement site remained relatively unchanged. The conclusions of the 6-year study indicate that the use of rubberized asphalt on Alta Arden Expressway resulted in an average four (4) decibel reduction in traffic noise levels as compared to the conventional asphalt overlay used on Bond Road. This noise reduction continued to occur six (6) years after the paving with rubberized asphalt. This degree of noise attenuation is significant, as it represents a 60% reduction in traffic noise energy, and a clearly perceptible decrease in traffic noise. This degree of traffic noise attenuation from rubberized paving is similar to the result documented in several non-related studies conducted in recent years at various other locations, both nationally and internationally. The conclusions of this study are based on tests conducted in Sacramento County on the Alta Arden Expressway and Bond Road. Attenuation provided by rubberized asphalt may vary in other locations with different climates and different percentages of medium duty and heavy duty trucks.   Table of Contents | Executive Summary | Introduction | History of Noise Reducing Pavement | The Process of Producing Rubberized Asphalt | Current Uses of Rubberized Asphalt | Tables | Studies of Rubberized Asphalt Outside of Sacramento County | Sacramento County Rubberized Asphalt Noise Studies | Conclusions of the Studies Conducted in Sacramento County | Appendix A - Acoustical Terminology | Appendix B - Noise Standards Commonly Applied to Projects in Sacramento County