Evaluating techniques for modeling buildings in the FHWA TNM

This paper investigates the impact of various building modeling techniques on predicted traffic noise levels in the Federal Highway Administration's (FHWA) Traffic Noise Model (TNM). In TNM, buildings can be modeled using two different approaches: building row objects or individual barrier objects. Each approach introduces variations in modeling choices, such as determining which sides of a building to include when using individual barriers, or deciding whether a building row should be positioned at the center or along one side of the building structure. Hypothetical, flat-world TNM models were developed to compare these different approaches and techniques. The results demonstrate that the choice of modeling technique can significantly influence predicted noise levels. Additionally, the analysis reveals substantial discrepancies in noise predictions between TNM versions 2.5 and 3.2. This research underscores the need for consistent modeling techniques across state Departments of Transportation (DOTs), and highlights the need for further study into the real-world applicability of these techniques. The paper concludes with a recommendation for the inclusion of more detailed building modeling capabilities in future versions of TNM.