United States Department of Transportation
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Abstract:This technical manual describes the Federal Highway Administration’s Traffic Noise Model (TNM) Version 3.2. Chapter 2 describes the process of determining noise emissions and levels at a reference location 15 m (50 ft) from the roadway or construction equipment noise source. This includes: the geometric discretizing of the project in the horizontal plane into elemental triangles, which are the basis for all other computations; the computation of vehicle speed/operational time and direction based on user inputs and TNM objects; and the determination of noise emissions based on measured levels at 15 m (50 ft), which are then converted to free-field at the same location. Chapter 3 describes how adjustments based on the horizontal geometry are determined. These include adjustments for: traffic volume and speed, and roadway lengths and distance (Ad). User-specified adjustment factors are also discussed. Chapters 2 and 3 combined describe the functions that depend on the horizontal geometry. Chapter 4 describes how adjustments for all shielding and ground effects between the roadway and the receiver (As) are determined. Chapter 5 covers additional adjustment factors for parallel and single barrier reflections. Chapter 6 covers the computation of contours. Appendices supplement the discussions as needed and are largely reproductions of the appendices found in the TNM Version 1.0, modified only to reflect changes between TNM 1.0 and TNM 3.2 and to avoid repetition of some materials already presented in the main body. New appendices have been added to cover the TNM basemaps and object intersection rules in TNM 3.2.
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