Supplemental Guidance on the Application of FHWA’s Traffic Noise Model (TNM) (2014) / Chapter Skim
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Pages 91-100
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91 C H A P T E R 1 3 13.1 Introduction Tunnel openings produce localized increases in traffic noise levels in relatively close proximity to the opening (or "portal")
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92 For the evaluation of these candidate modeling techniques, the team calculated traffic noise levels using SoundPLAN's tunnel-openings objects and algorithms and then used those calculated values as the baseline against which each modeling technique was evaluated. This process resulted in the development of methodologies to adjust the FHWA TNM output data to appropriately incorporate the effects of tunnel openings.
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93 Figure 62. Plan view of modeled geometry for tunnel measuring 15 by 6 by 30 m with three parallel and evenly spaced roads inside (with the 5-by-7 matrix of receptors)
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94 results for a receptor height of 4.5 m AGL are not shown herein, they very closely matched the results at the 1.5-m receptor height. Figure 63 shows TNM and SoundPLAN tunnel-only noise levels for this modeling technique for the 5-by-7 matrix of receptors at 1.5 m AGL.
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95 20 30 40 50 60 70 80 20 30 40 50 60 70 80 Ca lcu la te d Le q (d BA )
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96 20 30 40 50 60 70 80 90 Ca lc ul at ed T un ne lon ly L eq (d BA ) 5 x 6 x 30m Tunnel at 1.5 m AGL SoundPLAN Tunnel Only TNM Tunnel Only 20 30 40 50 60 70 80 90 Ca lc ul at ed T un ne lon ly L eq (d BA )
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97 -15 -10 -5 0 5 10 15 TN M L eq re : S ou nd PL AN L eq (d BA ) 5 x 6 x 30m Tunnel at 1.5 m AGL TNM Tunnel Only re: SP -15 -10 -5 0 5 10 15 TN M L eq re : S ou nd PL AN L eq (d BA )
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98 20 30 40 50 60 70 80 20 30 40 50 60 70 80 Ca lc ul at ed L eq (d BA )
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99 should be evenly spaced across the tunnel section along the full length of the tunnel, with two 30-m-tall noise barriers located along the tunnel walls: – Three roadways are suggested for single-direction tunnels, since most of the published research and the tests in this research were conducted with such a configuration. Each of the three roadways should have all of the traffic that was on the road outside of the tunnel (regardless of the number of lanes that were modeled outside of the tunnel)
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From page 100... ...
100 increased such that they are approximately seven to eight times the total traffic volume outside of the tunnel. This can be accomplished by either adding more roadways in the tunnel or by increasing proportionally the traffic volumes on the modeled roadways.
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