Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
6 1. INTRODUCTION Section 32801 of the 2012 surface transportation authorization act, Moving Ahead for Progress in the 21st Century (MAP-21), called for the U.S. Department of Transportation (USDOT) to conduct a comprehensive truck size and weight limits study. The law required the study to examine the effects of operation of large trucks in terms of impacts on bridges, pavements, safety, fuel efficiency, the environment, enforcement of truck regulations, and shares of freight traffic carried by trucks and other freight modes. The MAP-21 study charge to USDOT is included as Appendix A of this report. USDOT asked the Transportation Research Board (TRB) to provide a peer review of the study it carried out in response to this provision of the statute. To conduct the review, TRB convened a committee that includes members with expertise in highway safety, freight transportation economics, bridge engineering, pavement engineering, and highway safety enforcement. Membersâ biographies appear at the end of this report. The committee has delivered its review in two reports. The first report (TRB 2014) reviewed desk scans (literature reviews) prepared by USDOT in each of the technical areas of the USDOT study with respect to their thoroughness in identifying past research, assessing models and data for conducting the comprehensive study, and synthesizing the preceding body of work. This final report is the committeeâs review of the USDOT technical reports (USDOT 2015a, 2015b, 2015c, 2015d, 2015e, 2015f), which present estimates of five categories of impacts of changes in federal truck size and weight limits: effects on bridges, pavements, shares of total freight traffic carried by trucks and other freight modes, safety, and enforcement of truck regulations. The report on shares of traffic by freight mode also addresses environmental impacts, energy efficiency, and effects on shipper costs. USDOT describes the content and purpose of the technical reports as follows (Summary, ES-1): 1 1 In this report, for ease of reference, the volumes of the technical report are cited as follows: Bridge = USDOT 2015a, Compliance = USDOT 2015b, Safety = USDOT 2015c, Modal Shift = USDOT 2015d, Pavement = USDOT 2015e, and Summary = USDOT 2015f.
7 FHWA [the Federal Highway Administration] did not intend to develop or support a position on changes to current Federal truck size and weight limits in this study; rather, the agency intended to assess the impacts that any such changes might have in the various areas included in the study to better understand the impacts that trucks operating above current Federal truck size and weight limits have today. The study was set up to provide the results of the assessments that were completed and to provide a summary of this analysis to Congress. The committeeâs task statement (Appendix B of this report) requires the committee to comment on the extent to which the technical analysis and findings address the issues identified by Congress. At a public meeting of the committee on July 14, 2015, USDOT staff presented summaries of the technical reports and responded to questions from the committee. The meeting included an opportunity for members of the public to comment to the committee on its task. Appendix C acknowledges public comments that the committee received. This report was subject to an independent review according to the procedures of the National Academies of Sciences, Engineering, and Medicine, as described in Appendix D. The committee understands that the USDOT reportâs primary intended audience is Congress and that the reportâs purpose is to provide Congress with information about the consequences of any changes that it may enact in federal truck size and weight regulations. USDOT also recognizes other audiences for its report, as indicated by its outreach to state government, industry, and the public during the study. The states need information to guide their decisions about size and weight regulations, and members of the public wish to understand the possible effects of proposed changes in regulations. The committee assessed the USDOT study with respect to these intended audiences and purposes. Its review of each of the technical reports sought to answer a series of questions: Do the technical analysis and findings address the issues identified by Congress, is the methodology theoretically credible, and are the data adequate for carrying out the estimates according to the chosen method? The scope of the committeeâs review was limited. The committeeâs conclusions concentrate on
8 the principles of the methodologies used, the credibility of major results, the format of the presentation of results, and the overall structure of the USDOT study. With few exceptions, the committee did not attempt to verify data or computations described in the technical reports. Also, as the reviews of the technical reports below note, in some instances the reports do not give full details on methods and assumptions. The committee understands that additional documentation may be published later or will be available from USDOT, but it was unable to pursue documentation beyond the already published reports. The committee understands that USDOT does not plan substantial revisions to the technical reports. The committeeâs recommendations propose improvements that are suggested by the experience of the USDOT study and that could be adopted if USDOT, the states, or others undertake studies in the future. The recommended improvements would increase the usefulness of future studies to governments and the public as sources of information on the consequences of truck size and weight regulation. The next chapter of this report presents conclusions and recommendations concerning the USDOT study as a whole. The five subsequent chapters present conclusions and recommendations concerning the analyses in each of the technical reports: bridges, pavement, modal shift, safety, and enforcement. References Abbreviations TRB Transportation Research Board USDOT U.S. Department of Transportation TRB. 2014. Review of U.S. Department of Transportation Truck Size and Weight Study: First Report: Review of Desk Scans. March 31. http://onlinepubs.trb.org/onlinepubs/sr/TS&WDeskScans.pdf. USDOT. 2015a. Comprehensive Truck Size and Weight Limits Study: Bridge Structure Comparative Analysis Technical Report. June.
9 USDOT. 2015b. Comprehensive Truck Size and Weight Limits Study: Compliance Comparative Analysis Technical Report. June. USDOT. 2015c. Comprehensive Truck Size and Weight Limits Study: Highway Safety and Truck Crash Comparative Analysis Technical Report. June. USDOT. 2015d. Comprehensive Truck Size and Weight Limits Study: Modal Shift Comparative Analysis Technical Report. June. USDOT. 2015e. Comprehensive Truck Size and Weight Limits Study: Pavement Comparative Analysis Technical Report. June. USDOT. 2015f. Comprehensive Truck Size and Weight Limits Study: Volume 1: Technical Reports Summary. June.
