A STUDY OF THE US NCHRP TRAFFIC NOISE PREDICTION METHOD

The search for a comprehensive, accurate traffic noise prediction method generally applicable to Australian conditions has been continuing for some years now. To date most effort has been directed towards methods imported from the UK and the USA. Having earlier completed an extensive evaluation of the UK method, which was documented in part at the last ARRB conference, attention was focused on the US method. An evaluation of the Australian performance of the US NCHRP prediction method has recently been conducted utilising predicted and measured levels at 55 sites located variously in Queensland, Victoria and Western Australia. A sensitivity analysis of the method revealed that it responded predictably to changes in parameters such as traffic speed and volume but that it was restricted in application to speeds in excess of 60 km/h, to propagation distances in excess of 16.5 m and to noise barrier situations excluding the grazing incidence (barrier of zero height) condition. The method tended to underpredict noise levels. In the case of l10(1h) for example the mean underprediction was 0.9 db(a) with an accompanying standard deviation of 3.7 db(a). As was the case with the UK method evaluation, these results allowed specification of correction factors (based on the means) and accompanying accuracies (95 per cent confidence limits) of future NCHRP predictions. A set of alternative, but similar, correction factors and accuracies was also determined for the situation where users of the method may wish to allow a facade reflection correction of 2.5 db(a). An application based comparison of the performance of the UK and the US methods under Australian conditions was conducted. Generally, the US method was found to exhibit poorer accuracy in Australia than did the UK method. (Author/TRRL)

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  • Supplemental Notes:
    • This paper was presented during the 12th Australian Road Research Board Conference, Hobart, Tasmania, 27-31 August 1984.
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    ARRB

    Melbourne, Victoria  Australia 
  • Authors:
    • SAMUELS, S E
    • Fawcett, G
  • Publication Date: 1984

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 90-98
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  • Accession Number: 00393403
  • Record Type: Publication
  • Source Agency: ARRB
  • Files: ITRD, TRIS, ATRI
  • Created Date: Jun 30 1985 12:00AM