Long-term noise performance of open graded asphalt concrete (OGAC)—Results of 10-year long study

During June and July of 1998, an open grade asphalt concrete (OGAC) pavement overlay was applied to a 5.6-mile (9-kilometer) stretch of aged dense graded asphalt concrete (DGAC) along Interstate 80 to the east of Davis, California. Beginning in 1998, noise conditions have been monitored by Illingworth & Rodkin as part of an ongoing study conducted by the California Department of Transportation (Caltrans) to evaluate the long-term effects of highway pavement types on traffic noise. Noise evaluation of the OGAC pavement was conducted using the continuous flow traffic time integrated method (CTIM) of measuring traffic noise levels at locations adjacent to the roadway and the on-board sound intensity (OBSI) method of measuring tire-pavement noise close to the tire-pavement interface. Measurements were conducted on more than 70 days over the past 10 years, resulting in a total of more than 275 hours of noise measurements and generating an extensive data set. This paper focuses on the results of the OBSI and CTIM measurements. Results discussed in this paper include; 1) a comparison of the acoustical performance of the OGAC pavement to the baseline DGAC and other pavement types, 2) a description of the effects of aging of the OGAC pavement on acoustical performance, and 3) a description of seasonal trends in noise levels based on the data set. Based on the noise measurements, the OGAC pavement initially resulted in noise levels that were about 7 dB below those measured for the baseline DGAC pavement and maintained these quieter characteristics through 10 years, with only a slight increase in noise levels over time.