Truck Size and Weight Limits Research Plan Committee: First Report: Candidate Research Topics; Framework for Setting Priorities (2018) / Chapter Skim
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3. RESEARCH AND DATA RECOMMENDATIONS OF PAST STUDIES
3. RESEARCH AND DATA RECOMMENDATIONS OF PAST STUDIES
Pages 6-15
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and 1981 (FHWA 1981) , and earlier TRB committee studies, including TRB Special Report 225, Truck Weight Limits: Issues and Options (TRB 1990)
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freight flow database to provide estimated county-level freight flows by mode Regularly collect data on shipping rates for freight carried by truck Bridges Model the effect of changes in truck size and weight limits on bridge decks, using data from USDOT's Long-Term Bridge Performance Program Develop a method to estimate the effects of changes in limits on bridges on local roads Pavement Model the effect of changes in truck size and weight limits on pavements with overlays Collect data on local road pavement characteristics and truck traffic to support estimates of the effect of changes in limits on local roads ========================================================================== USDOT's recommended activities are in four categories: Adjustments or additions to existing data collection programs (truck weight in crash records; expanded WIM data; weight recording in inspection records; enforcement cost data; truck traffic data in the Long-Term Bridge Performance [LTBP] program; local bridge, pavement, and traffic data)
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. The TRB committee that USDOT asked to review the Comprehensive Truck Size and Weight Study's technical reports was not charged with proposing a comprehensive research agenda for future truck size and weight studies.
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Structure of Future Truck Size and Weight Studies Future truck size and weight studies should evaluate the full range of methods for mitigating the costs of truck traffic, including: – Size and weight limits – Vehicle design (as affecting stability and vehicle–infrastructure interaction) – Bridge and pavement design and management – Enforcement – Permit and fee systems The objective of evaluations should be to identify strategies to reduce the public costs and increase the benefits of highway freight transportation Methods for Impact Estimates in Future Truck Size and Weight Studies Base bridge cost estimates on explicit assumptions about state highway agency responses to changes in truck traffic Estimate pavement and bridge impacts from valid samples of actual pavements and bridges Research Test alternative forms of mode choice models Continue three research efforts begun in the 2016 USDOT truck size and weight limits study: – Weigh-in-motion-derived traffic data – Relationship of crash frequency on a road to traffic volume and vehicle type mix – Relationship of weight enforcement effort to violation rate =========================================================================== The information systems to which the committee referred are those maintained by the states and federal government for basic asset management purposes: states' asset management and safety management information systems, and federal and state data systems that support research, regulation, and planning (see Box 3)
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National Highway Traffic Safety Administration Trucks in Fatal Accidents (TIFA) program State crash record systems =========================================================================== The 2015 TRB committee's recommendations also concerned the structure of future truck size and weight limit evaluations (TRB 2015, 4)
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Earlier Truck Size and Weight Studies The gaps in data and understanding that the 2016 USDOT study identified were recognized in earlier truck size and weight studies. The previous USDOT evaluation, published in 2000, included a list of research needs that considerably overlaps the 2016 list (see Box 4)
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in response to a congressional directive for a study of the federal regulation of truck sizes and weights and for recommendations on appropriate revisions. The TRB committee report reviews the major past studies of size and weight limits by the federal government, TRB, and others.
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Conclusions (in part) : Appropriate objectives for size and weight regulations include to improve safety, to allow efficient commerce, to establish highway design parameters, to manage consumption of infrastructure The methods of past studies have not produced satisfactory estimates of effect of changes in truck weights on bridge costs Models and data will never be adequate to predict the outcomes of regulatory changes with high confidence Research and monitoring needed to understand the relationship of truck characteristics to highway costs are not being conducted Monitoring of compliance is too unsystematic to allow the costs of noncompliance to be estimated Recommendations (related to research)
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As noted above, the TRB committee that authored the report Regulation of Weights, Lengths, and Widths of Commercial Motor Vehicles concluded that projections of the outcomes of regulatory changes based solely on experience with vehicles currently in commercial use could never be highly reliable and recommended a program of pilot studies as a more definitive means to evaluate changes in truck size and weight regulations. The report outlined administrative arrangements for such a program (TRB 2002, 200–203)
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These include state highway agencies' traffic, crash, and vehicle weight databases and asset management systems, as well as national research and monitoring data systems such as the National Highway Traffic Safety Administration (NHTSA) crash databases, the Carload Waybill Sample, and the VIUS.
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