The final rule on 23 CFR 772: Procedures for Abatement of Highway Traffic Noise and Construction Noise, dated July 13, 2010, immediately eliminated the use of the TNM Lookup Tables in either form to predict noise levels on Federal or Federal-aid projects. The FHWA developed the Lookup tables to provide TNM users with a simple screening tool for highway analyses. The tables were to supplement TNM to obtain quick estimates. The intended use of the estimates was to inform planners about the potential scope of their project, or to educate the public. The Lookup Tables were not intended to be a substitute for the TNM or for routine use in performing a noise analysis. Many practitioners started using the Lookup Tables due to long calculation times inherent with the use of the FHWA TNM when compared with the previous model. However, the dramatically increased speed of computers currently available on the market reduces the model run times to a fraction of what could be accomplished a few years ago. Further, a narrow interpretation of the final rule requiring the use of the FHWA TNM version 2.5 eliminated the option to use the TNM Lookup Tables. Use of the TNM Lookup Tables continued as a legacy. The FHWA clarified through this final rule that the TNM Lookup Tables are not an acceptable model for use on Federal or Federal-aid highway projects. The FHWA will not update the TNM Lookup Tables for future versions of the FHWA TNM.
The following documents were associated with the FHWA TNM Version 2.5 Look-Up Tables: