What is Average Pavement? A Critical Commentary

The Traffic Noise Model (TNM) is used to forecast traffic noise levels. When applied to federally funded projects, a user of the software is expected to apply "average" noise emissions for pavements. This "average" is an intermediate value that in some manner falls in between the higher noise emissions of Portland Cement Concrete (PCC) and lower emissions of Dense Grade Asphalt Concrete (DGAC). The purpose of this paper is to illustrate some curious characteristics of "average" pavement as it is employed in the TNM. Among these characteristics are what appear to be different methods for averaging the noise emissions for various vehicle types, such as automobiles, medium trucks, and heavy trucks. The inquiry concludes with an attempt to clarify exactly what constitutes an "average" when it comes to pavement noise emissions..