Supplemental Guidance on the Application of FHWA’s Traffic Noise Model (TNM) (2014) / Chapter Skim
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31 C H A P T E R 4 Area sources include weigh stations, park-and-ride lots, toll facilities, and service plazas. Typical noise sources near these facilities include low-speed and stop-and-go traffic, accelerating vehicles, decelerating vehicles, and idling trucks.
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32 involving standard TNM vehicle types, although it is expected to be most commonly used for heavy trucks idling either at weigh stations or for extended periods at service plazas. 4.1.2.1 Roadway Segments The standard approach utilizes TNM roadway segments to represent stationary noise sources.
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33 4.1.2.3 Line Sources In some cases, it may be unnecessary or impractical to model each stationary noise source as a separate TNM roadway. For example, different spaces within a row of parking slots at a truck stop may be used at different times throughout the modeled time period.
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34 and C (the minimum emission level at very low speeds) is set to the measured emission level at 50 ft.
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35 in length from 10 ft to 180 ft, and the Area C roadway segment grows from 175 ft to 280 ft. As a result, the volume factors also change: ( )
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36 4.1.4.5 Example 5 A practitioner needs to model the truck stop shown in Figure 29. With all delineated spaces full, the facility has a capacity of 98 heavy trucks.
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37 • Using Table 7, determine the appropriate modeled speed for each ZOI roadway. Note that although each ZOI does not need to be modeled as a separate roadway, care must be exercised to ensure that the appropriate speeds are assigned only to the correct roadway segments.
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38 determined from field measurements during TNM's development, while vehicles are accelerating. 4.2.2.1 Entrance Ramps When using the flow control feature to model traffic departing from weigh stations, park-and-ride lots, service plazas, and other similar facilities on entrance ramps to limited-access roadways, the following input parameters are recommended on TNM's flow control tab: • Control Device: Onramp.
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39 the queue may be determined by direct observation. For future facilities, the number in the queue may be computed based on the average length of the queue26 or upon projected traffic volume combined with the average waiting time in the queue.27 • Compute the modeled volume.
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