Porous Elastic Road Surface As An Ultimate Highway Noise Measure.

Highway traffic noise in urban areas of Japan is a serious problem, not only for residents along highways, but also for highway administrators. Only 13 percent of urban highways have met the environment standard for noise. Noise barriers cannot be used as a noise countermeasure on the majority of highways on which access is not controlled. Noise levels of areas along some urban highways exceed the standard by 15 dB(A) or more. This problem is impeding new highway construction in urban areas. Porous asphalt pavement has recently been introduced on urban highways in Japan. Its noise reduction effect of 3 dB(A) is insufficient, because it only improves the noise environment satisfaction rate by a few percent. Furthermore, the durability of its noise reduction effect usually seems to be only three years, which is shorter than its life-cycle as pavement. The Public Works Research Institute (PWRI) has, since 1993, been developing a new low-noise pavement named "Porous Elastic Road Surface" (PERS). This new pavement has a porous structure composed of granulate rubber made from old used tires as its aggregate and urethane resin as its binder. Its porosity is approximately 40 percent. The pavement was first proposed in Sweden in the 1970s, however, Swedish researchers have failed to improve it as a practical pavement. Noise reduction levels are 15 dB(A) for cars and 8 dB(A) for trucks. The author estimates that the potential noise reduction levels in Leq exceed 10 dB(A). More than 90 percent of highways in urban areas would meet the standard if this noise reduction level were achieved. The PWRI has already solved several of the problems with PERS, for example, insufficient adhesion between the pavement and the base course, low skid resistance, and its poor fireproof performance. Its technical level has already reached the stage of test construction on urban highways. This paper examines the general performance of PERS obtained through past development at the PWRI. It also summarizes the results of recent research done to further improve the noise reduction levels of PERS and the first test construction using PERS in Japan. The final noise reduction target for any type of vehicle is between 15-20 dB(A). The author expects that PERS will reduce highway traffic noise problems in urban areas of Japan to a minor, negligible level in the near future. For the covering abstract see ITRD E135448.