Road traffic noise prediction model "ASJ RTN-Model 2023": Report of the Research Committee on Road Traffic Noise

BackgroundIn 1974, the Acoustical Society of Japan first organized a research committee to develop a road traffic noise prediction model.This committee has been continuously undertaking research activities since then with the aim of developing an adequate prediction method for road traffic noise on the basis of state-of-the-art knowledge in response to the demands of trends [1].As a result of its activities, a prediction model called ASJ Model 1975 was published in 1975, which provided a method of calculating the 50-percentile A-weighted sound pressure level (LA50) [2,3].This model was widely accepted and applied to assessments of noise around roads for many years.After that, research activities continued, improving the accuracy of prediction and expanding the scope of its application [4][5][6].In parallel with these activities, from 1988, the committee worked on the development of a new prediction method based on the equivalent continuous A-weighted sound pressure level (LAeq).The outcomes of the research were summarized, and the calculation model (ASJ Model 1993) was published in 1994 [7].This model introduced general procedures for the calculation of LAeq at roads with a uniform cross-sectional structure.Afterwards, there was a substantial change in the environmental administration concerning noise.In June 1997, the "Environmental Impact Assessment Law" was promulgated, whose enactment was based on the "Environment Basic Law" (the law revising the "Basic Law for Environmental Pollution Control", which was issued in November 1993), and it was enforced in June 1999, two years after its promulgation.In addition, the "Environmental Quality Standards for Noise" (enacted in 1971) was revised in September 1998 and enforced in April of the following year.In the standards, LAeq was adopted in place of LA50 as the noise index for road traffic assessment.At the same time, the standard values for general residential areas and areas facing roads were renewed.Corresponding to these changes, the above-mentioned ASJ Model 1993 was later developed further on the basis of the results of a surveillance study, and ASJ Model 1998 was introduced in April 1999 as a new model based on LAeq assessment [8].The model had an expanded scope of application to cover almost all types of roads and structures, including general roads and special road sections, such as interchanges, road tunnels, semi-underground roads, and overhead/double-deck viaducts.In addition, the structureborne noise of viaduct roads was newly included in this model.Shortly after its report, further research activity was started with the aims of expanding its field of application, introducing wave-based computational methods for sound propagation, and improving prediction accuracy.As a result,