SPECIFIC DIFFERENCES BETWEEN THE "REVISED DESIGN GUIDE" AND THE TWO AUTHORIZED NOISE PREDUCTION METHODS OF THE FHWA

Three noise prediction methods (composite of NCHRP Reports 117/144; Transportation Systems, TSC; and the revised design guide, RDG) are coalesced into a common framework to enable users of these methods to compare the physical assumptions of the methods step by step in the calculation logic, and to anticipate how RDG will change the predicted noise levels relative to those predicted by 117/144 and TSC. The common framework consists of 3 graphs and 2 equations that coalese the three methods into the following logic: emission levels of individual vehicles at 50 ft. (15.25); to the energy-mean A-level at 50 ft., from the entire stream of traffic; to the L sub eq at any distance D; and finally, to the 10-percentile A-level at this distance (ad hoc adjustment necessary in the 117/144 method). Three examples using the common framework are described. Differences among the models center around the improved RDG predictions at low VD/S, the inclusion of medium trucks in the RDG method, and the flexibility in the rate of divergence (-d dB/DD to -4.5 dB;DD) in the RDG method. Tables summaries the major differences between the methods. With each change is tabulated the associated circumstances. Changes of 10 dBA are realtively prevalent in the tables while extreme changes of 15 dBA are rare.

Media Info

  • Features: Figures; Tables;
  • Pagination: p. 29-39
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00131397
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: May 14 1976 12:00AM