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Pavement Effects Implementation Study

5. Conclusions

For the FHWA TNM Pavement Effects Implementation Study, three implementation options were considered:

  1. integrating new data into the FHWA TNM vehicle noise database ( REMEL) for specific pavement types and also adjusting the roadway effective flow resistivity (EFR, a measure of sound absorption);
  2. adjusting the existing tire/pavement source level in the FHWA TNM using on-board sound intensity (OBSI) data and also adjusting the roadway EFR; and
  3. applying a pavement type offset adjustment value to the predicted sound levels (post FHWA TNM calculations).

Investigations of pavement-specific REMELs, OBSI-adjustments, and EFR-adjustments allowed for the determination of the validity of each option.

Implementation Option 1 was determined to be a valid option for implementing pavement-specific effects in the FHWA TNM, assuming the REMEL data set collected is adequate, as described in Appendix B.  Adequacy is determined based on the number of data points, number of sites represented, range of speeds, and tonal qualities of the average spectrum.  Prior to implementation, further work required for this option includes the following:

Although this option would require extensive cost- and time-prohibitive data collection in order to generate a database for the FHWA TNM for a broad array of pavement types, this option should be left open to FHWA TNM users; they would need to get FHWA approval prior to implementation.

Implementation Option 2 was determined to be a valid option for implementing pavement-specific effects in the FHWA TNM.  Prior to implementation, further work required for this option includes the following:

Because a large OBSI database already exists and is relatively efficient to augment, it is intended that the adjustment database will be included in a future version of the FHWA TNM.  In addition, user-defined OBSI adjustments should be an option for FHWA TNM users; they would need to get FHWA approval prior to implementation.

Implementation Option 3 was determined  not to be a valid option since current efforts established that pavement effects are distance-dependent and site-geometry dependent, and therefore, adjusting predicted sound levels by a single decibel offset or adjustment value would be inaccurate in many cases.

The FHWA finds both Implementation Options 1 and 2 to be valid options for users, but Implementation Option 2 (using OBSI data to adjust for pavement effects) is the preferred option due to ease and efficiency of data collection, compilation, and implementation.  It should be noted that both Implementation Options 1 and 2 would be dependent on FHWA policies or guidance and would require a change to federal noise policy 23 CFR 772.

Updated: 04/26/2012
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