Download Cost-benefit Analysis Book in PDF, ePub and Kindle
"EXECUTIVE SUMMARY: At highway speeds, the major source of noise is the interaction between tires and the road surface. Noise barriers have been used by state transportation departments for many years and are the preferred solution for reducing highway traffic noise. Federal Highway Administration regulations for highway traffic and construction noise abatement are included in the Code of Federal Regulations (23 CFR772)1 and currently only consider noise barriers as an abatement measure for highway noise. However, pavement type can considerably reduce the noise generated from tire-road interaction. Yet considering pavement as a noise abatement measure is currently only allowed for pilot projects approved by the Federal Highway Administration. Through the end of 2010, 47 state departments of transportation and the Commonwealth of Puerto Rico have constructed more than 2,748 linear miles of barriers at a cost of close to 5 .5 billion (in 2010 dollars)2 . Treatment of highway pavement is generally less costly than the construction of barriers, but the noise reduction achieved by a quieter pavement is typically less than the reduction from a well-designed barrier, at least for residents in the immediate vicinity of the barrier. However, quieter pavements produce a reduction of noise at the source, which means that it may be possible to increase the number of benefited receptors (the recipient of an abatement measure that receives a noise reduction at or above the highway agency's chosen noise impact threshold value). A combination of barrier and pavement treatment may lead to cost-effective solutions to highway noise. To evaluate effectiveness of quieter pavements, a reliable measurement method for tire/road noise is needed. The method that is currently favored is measuring On-Board Sound Intensity (OBSI). OBSI data are collected in conformance with AASHTO TP-76,3 the American Association of State Highway and Transportation Officials Standard Method of Test for Measurement of Tire/Pavement Noise Using the On-Board Sound Intensity (OBSI) Method. A workshop on cost-benefit analysis of noise barriers and quieter pavements was held on January 16, 2014. One objective of the workshop was to evaluate the National Cooperative Highway Research Program Report 738, "Evaluating Pavement Strategies and Barriers for Noise Mitigation". Report 738 was prepared under Project 10-76, and is typically referred to as NCHRP 10-76.4 The report describes a methodology for the evaluation of both barriers and pavements for noise abatement, and explores how quieter pavement technology can be incorporated into Federal and state noise policy. Three key elements of the method presented in NCHRP 10-76 involve life cycle cost analysis (LCCA), the use of a research version5 of the Federal Highway Administration Traffic Noise Model (TNM), and a method for the evaluation of tire pavement noise reduction, OBSI. This report contains summaries of the presentations given during the workshop and the results of discussions identifying the challenges presented by implementing the NCHRP 10-76 methodology, especially to state departments of transportation, which carry out noise abatement projects in cooperation with the Federal Highway Administration and in conformance with the federal requirements in 23 CFR772. Using LCCA, planners can evaluate the initial cost of abatement using pavement and barriers as well as rehabilitation and maintenance costs. The methodology also incorporates a measure of the effectiveness of the resulting predicted level of traffic noise. Current regulations require impact determination and barrier design to be completed with the public-release version of TNM and average pavement. By using a research version of TNM and OBSI data to refine the tire-pavement interaction noise source, pavement effects could be included in the model (and therefore predictions could be more accurate and pavement type can be considered when assessing noise impact and abatement). Several examples illustrated that the NCHRP 10-76 approach can be successfully applied to real highway project studies. In some situations, a barrier-and-pavement hybrid solution can be more acoustically effective and/or cost effective than a barrier only solution and can allow for additional benefited receptors where a barrier only solution would not be feasible and/or reasonable. Both current regulations and the public- release version of TNM require modification if the noise reduction benefits of pavements are to be realized in construction projects. The noise reduction achieved by sound propagation over sound-absorptive pavement could also be included in the public-release version of TNM. An important part of the workshop, which was attended by noise barrier and pavement experts, as well as representatives from the FHWA and state departments of transportation, was to discuss the challenges of implementing NCHRP 10-76 methodology to state departments of transportation and to develop findings and recommendations based on these discussions. The key elements of these discussions are presented in Chapter 3 of this report. The following recommendations appear in Chapter 4 of this report: Develop and document a noise evaluation process that accounts for both noise barriers and quieter pavements. Provide funding and implement the method presented to evaluate the abatement options on a pilot program basis to help evaluate and improve the process. Upgrade the public release version of TNM to include the OBSI-related pavement assessment capabilities currently available in the research version of TNM. Organize and make publically available national databases for OBSI and LCCA. Expand TNM and highway noise abatement training to include consideration of quieter pavements and enable use of the research version of TNM. Encourage FHWA to develop guidance on the use of quieter pavements and barriers for noise abatement. Incorporate noise performance into a new performance management system. Develop and provide a noise abatement training program for pavement engineering staff. Other presentations from the workshop with important background information relevant to cost benefit analysis, noise barriers, and quieter pavements are summarized in Appendix A. The workshop agenda, the names of the participants, definitions of terms and a list of acronyms are provided in Appendix B, Appendix C, and Appendix D."
