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4 INTRODUCTION Section 32801 of the 2012 surface transportation authorization statute, Moving Ahead for Progress in the 21st Century (MAP-21), calls for the U.S. Department of Transportation (USDOT) to conduct a comprehensive truck size and weight limits (CTSW) study. The law requires 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 CTSW study. To conduct the review, TRB convened a committee that includes members with expertise in highway safety, vehicle dynamics, freight modal shift, bridge and structural analysis, pavement design, and highway safety enforcement. Membersâ biographies appear at the end of this report. The committee is to deliver its review in two reports. This first report reviews desk scans (literature reviews) prepared by USDOT in each of the technical areas of the CTSW study with respect to their thoroughness in covering the literature, analysis of models and data for conducting the comprehensive study, and overall synthesis of the preceding body of work as it applies to the study that is to follow. Once USDOT has completed the technical analysis for the study in spring 2014, the committee will prepare its second report, which will comment on the extent to which the technical analysis and findings address the issues identified by Congress. Appendix B contains the committeeâs task statement. The committee examined 10 documents provided by USDOT (USDOT 2013aâ2013j): desk scans and project plans for each of five categories of impacts of changes in federal truck size and weight limits: effects on bridges, pavements, safety, enforcement of truck regulations, and shares of total freight traffic carried by trucks and other freight modes. [The modal shift desk scan (USDOT 2013c) and project plan (USDOT 2013h) address environmental impacts and energy efficiency as well as mode shift.] In addition, at a public meeting of the committee on December 5, 2013, USDOT staff presented summaries of the desk scans and project plans and responded to questions from the committee. That meeting was open to
5 the public and included opportunity for public comment to the committee on its task. Appendix C acknowledges public comments received on the study. This report was subject to an independent review according to the procedures of the National Research Council, as described in Appendix D. The desk scans describe methods and results of past studies of effects of changes in truck size and weight limits and models and data sources useful for these analyses. The project plans outline the methods to be used in the CTSW study to estimate each category of impact. As the committeeâs task statement specifies, this report reviews the desk scans. The committee had to understand the project plans to judge whether the desk scans were providing adequate support for the intended analyses. This report includes observations on whether the coverage of the scans is consistent with the requirements of the project plans. USDOT faces significant time and resource constraints in completing the CTSW study. The final contractor study team was selected in 2013, technical analyses are to be completed in spring 2014, and the study report is to be delivered to Congress by November 2014. However, the USDOT study team asked that the TRB committee not refrain from noting gaps or other shortcomings in the technical analyses even if they appear justified in light of the study schedule. USDOT staff also informed the committee that, in consideration of the constraints on the present study, the USDOT report may indicate directions for improvement in future analysis of impacts of size and weight regulations. Consistent with this USDOT study goal, some of the committeeâs comments may propose actions that are not feasible in the present study but that might be applied in later analyses. The next section of this report presents comments that apply to the desk scans in general. The following five sections present comments on each of the desk scans: bridges, pavement, modal shift, safety, and enforcement. The comments on each of the topical desk scans respond to the following questions, which are derived from the committeeâs task statement: ï· Is the desk scan thorough? ï· Is it missing literature, case studies, models, or data that would help achieve the study goals?
6 ï· Does it interpret the literature reviewed correctly? ï· Does it synthesize the literature and draw appropriate conclusions? The committee intends its review to help USDOT in meeting the congressional study charge and in producing a technical analysis that is useful to the public as a source of information on the consequences of truck size and weight regulation. References Abbreviation USDOT U.S. Department of Transportation USDOT. 2013a. Bridge Structure Comparative Analysis: Final Draft Desk Scan. Nov. USDOT. 2013b. Pavement Comparative Analysis: Final Draft Desk Scan. Nov. USDOT. 2013c. Modal Shift Analysis: Final Draft Desk Scan. Nov. USDOT. 2013d. Highway Safety and Truck Crash Comparative Analysis: Final Draft Desk Scan. Nov. USDOT. 2013e. Enforcement and Compliance Comparative Analysis: Final Draft Desk Scan. Nov. USDOT. 2013f. Bridge Structure Comparative Analysis: Final Draft Project Plan/Schedule. Nov. USDOT. 2013g. Pavement Comparative Analysis: Final Draft Project Plan/Schedule. Nov. USDOT. 2013h. Modal Shift Analysis: Final Draft Project Plan/Schedule. Nov. USDOT. 2013i. Highway Safety and Truck Crash Comparative Analysis: Final Draft Project Plan/Schedule. Nov. USDOT. 2013j. Compliance Comparative Analysis: Final Draft Project Plan/Schedule. Nov.
