It is suggested that different headway distributions are the reason for differences in the predicted barrier performance using a Monte Carlo random snapshot model and a "time history" method. The authors use the random method to derive an expression for the headway distribution assuming that the initial headway follows a negative exponential distribution. The transcendental equation can be solved by an iterative technique incorporated into the computer model. Possible errors arising from an incorrect choice of the initial headway are examined. It is shown that the random snapshot method, with the wrong initial headway, predicts a higher noise level that that estimated by the time history method. Use of an incorrect headway distribution can lead to an overestimation of barrier attenuation by approximately 1.5 db(a). Errors can be greatly reduced by using two different equations, one for the initial headway and a separate equation for the remainder. (TRRL)

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    Academic Press Incorporated

    24-28 Oval Road
    London NW1 7DX,   England 
  • Publication Date: 1979

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Filing Info

  • Accession Number: 00311738
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD, TRIS
  • Created Date: Oct 27 1980 12:00AM