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15 understanding of costs and benefits of changes in truck size and weight limits. Other countries have used trials and pilot studies as techniques to further improve confidence in understanding the impacts of new vehicle types. CANDIDATE RESEARCH PROBLEM STATEMENT TOPICS The elements of the committeeâs research roadmap will be problem statements specifying the research necessary for improving projections of the impact of changing size and weight limits. The committee has compiled the lists of candidate research problem statement topics in this section from various sources, including the experience and recommendations of past USDOT truck size and weight studies and research recommendations of past TRB committees. All of the topics refer to research to produce results that could be applied to reducing uncertainty in evaluations of changes in truck size and weight limits. The committee has presented its lists of candidate research problem statement topics for discussion by panels of experts in a series of public webinars. In formulating its research plan, the committee will consider the comments received in the webinars, any other comments received from the public, and the criteria described in the section below on setting research priorities. The committee has not yet reached a conclusion about research topics to be included in its research plan. Pavement and Bridge Research The candidate research problem statement topics identified by the committee for pavement research (see Box 6) and bridge research (see Box 7) are aimed at reducing the sources of uncertainties in impact estimates of infrastructure costs of changes in the limits that were identified in the USDOT 2016 study, the TRB committee review of that study, and the 2002 TRB committee report Regulation of Weights, Lengths, and Widths of Commercial Motor Vehicles. These include the need for methods applicable to the entire network of local roads and state highways that would be exposed to traffic of new vehicles, the
16 ability to predict the impacts of vehicles that differ greatly from common existing vehicles, credible methods for estimating the costs of projected physical impacts, and evaluation of the effects of truck platooning. =========================================================================== BOX 6 Candidate Research Problem Statement Topics: Pavement Impacts of Size and Weight Limit Changes 1. Determine the capability of current methods to produce appropriate pavement designs if trucks with maximum axle weights and configurations substantially different from the present ones come into use. Identify the most appropriate techniques for such applications. 2. Develop a method of projecting pavement performance that accounts for the characteristics and distribution of tire contact stresses, which may not be captured by AASHTOWare Pavement ME (the pavement design software that was applied in the pavement evaluation in the 2016 USDOT truck size and weight study). 3. Develop performance prediction models that allow consideration of the effects of changes in truck size and weight limits, as well as changes in the axle configuration, and that are applicable to the common types of actual pavements, including overlay pavements, on U.S. roads. 4. Evaluate the effect of dynamic loading on pavements and the relation of dynamic loading to the effect of truck traffic on pavement life. 5. Develop a method of predicting the increase in pavement distresses in local roads (and associated costs) due to changes in truck size and weight limits, taking into account limited data availability and variability in local highway agenciesâ construction and maintenance practices. 6. Demonstrate methods for taking into account uncertainties in pavement analysis and design in decision making on truck size and weight limits and for communicating the reliability of estimates to decision makers. Pavement analysis and design have many inherent uncertainties, such as uncertainties in material characterization and in weigh-in-motion data collection. 7. Develop methods to project how the adoption of heavier vehicles would impact pavement service life, cost, and environment through life-cycle assessment. The heavier vehicles will develop higher structural responses within the pavement; however, the number of load repetitions is expected to decrease for a given quantity of goods carried. 8. Assess how truck platooning (through the application of connected vehicle technology) would affect pavement performance and costs and how such effects can be controlled. 9. Determine the impact of changes in truck loading and axle configuration in unbound layers of pavements, especially on low-volume roads. ===========================================================================
17 =========================================================================== BOX 7 Candidate Research Problem Statement Topics: Bridge Impacts of Size and Weight Limit Changes 1. Survey state highway agencies to determine: (a) how states prioritize bridge deck treatment, repair, and rehabilitation or replacement; (b) how states prioritize bridge rehabilitation or replacement; and (c) highway agency unit costs and expenditures for deck overlays, deck replacement, bridge replacement, bridge strengthening, and bridge repair. 2. Survey local highway agencies to determine how the agencies make decisions to maintain, repair, rehabilitate, or replace bridges, and agency unit costs and expenditures for each. 3. Develop a description of present axle and gross weight distributions, axle configurations, and overload frequencies to the extent that available weight data allow. State- or region-specific data would be developed if needed according to impact modeling sampling plans. 4. Develop a model of the effect of truck traffic characteristics on bridge deck deterioration that is based on the observed relationship between deck performance and vehicle loads on a sample of bridges over time. 5. Develop a model of the effect of truck traffic characteristics on bridge deck deterioration that does not require field measurement of deck performance and loads. 6. Develop a method of estimating user costs of traffic disruptions caused by bridge posting and construction. 7. Develop a model of the effect of truck size and weight changes on bridge structure useful life. 8. Develop a method for estimating the change in bridge system life-cycle costs caused by changes in bridge loads arising from changes in truck size and weight regulations, based on the models and data produced in research on topics 1 through 7. 9. Develop a replacement for the âFormula Bâ provision in federal size and weight law that more appropriately controls the weight of short heavy vehicles. The research may involve determination of optimum axle configurations, considering shipper costs and infrastructure costs. 10. Develop safety standards for bridge barriers and deck overhang for trucks over 80,000 lb. gross weight. 11. Develop a method for establishing appropriate shares of bridge construction and repair cost responsibility for classes of trucks, including trucks currently operated under special permit, illegally overloaded trucks, and new truck types that may be adopted with changes in limits. 12. Assess how truck platooning would affect bridge loadings, performance, and costs. =========================================================================== Safety Research The candidate safety research problem statement topics are organized in two parts: targeted comparative evaluations of the safety performance of truck configurations (see Box 8) and long-term monitoring programs (see Box 9). Each part is structured in a sequence: development of study designs, development and testing of data collection methods, and conduct of the safety evaluations.
18 =========================================================================== BOX 8 Candidate Research Problem Statement Topics: Safety Consequences of Size and Weight Limit Changes Part 1: Targeted Comparative Evaluations of the Safety Performance of Truck Configurations Targeted comparative evaluations are research studies intended to compare the safety performance of a baseline truck configuration (a configuration now in general use) to one or more larger and/or heavier configurations. Data would be from a limited geographical area where the configurations are operating, and for a limited time period. The objective would be to measure relative crash involvement rates and crash severity for the configurations while controlling for roadway, operator, and other characteristics that affect safety performance. 1. Develop study designs for comparative evaluations This research will develop study designs for the comparative evaluations, described in Problem Statements 4, 5, and 6. Each study design would specify the following: (a) the research hypotheses to be tested (concerning relative safety performance of the configurations) and the precision necessary for the intended policy application; (b) data elements required and sample size; and (c) data analysis method to be applied. 2. Develop crash data enhancement procedures for research application This research will develop methods to enhance crash data by adding information on the weight and configuration of crash-involved trucks. The methods would meet the requirements of the study designs developed in the research outlined in Problem Statement 1, and would be applicable to the targeted comparative evaluations described in Problem Statements 4, 5, and 6. The research would test methods for obtaining weight data, which may include use of weigh-in- motion data and trucking company dispatch records. It would test methods to improve the ability of investigating officers to obtain configuration data through training and the use of supplemental forms. Finally, it would test administrative arrangements among government agencies and private firms for assembling data. 3. Develop exposure estimation procedures for research application This research will develop methods to obtain exposure data (including vehicle-miles of travel) with necessary details on weight, configuration, and other characteristics of travel of crash-involved trucks. The methods would meet the requirements of the study designs developed in the research described in Problem Statement 1 and would be applicable to the targeted comparative evaluations described in Problem Statements 4, 5, and 6. The research would test methods of acquiring weight data from existing enforcement activities and WIM installations and from special automatic data collection installations, develop sampling strategies, and test administrative arrangements for data collection. 4. Conduct route-based or network-based comparative evaluation This research will conduct a comparative evaluation through the observation of crash frequency and vehicle-miles of travel of truck configurations for one route or for a network of routes. The problem statement will be generic, that is, not specifying the configurations to be compared or the location of the routes. The research may be repeated for the same trucks in multiple jurisdictions or for different configurations in the same or multiple jurisdictions. The research will follow a study design
19 developed in the research described in Problem Statement 1 and use data collection methods developed in the execution of Problem Statements 2 and 3. 5. Conduct case-control comparative evaluation This research will conduct a comparative evaluation using the case-control study design. Crashes of trucks of interest (e.g., multi-trailer configurations or trucks exceeding normal weight limits) will be identified as they occur on a specified set of roads within a specified time period. The trucks in these crashes constitute the âcasesâ in the methodology. Following each crash, a control sample of trucks will be observed at the site of each crash. Characteristics of case and control trucks will be compared, using appropriate statistical methods. The problem statement will be generic, that is, not specifying the configurations to be compared or the location of the routes. The research will follow a study design developed in the research described in Problem Statement 1 and use data collection methods developed in the execution of Problem Statements 2 and 3. The study design will focus on how case crashes will be identified and how control crashes will be selected in an unbiased fashion. 6. Conduct comparative evaluation with trucking company data This research will conduct a comparative evaluation, performed with data for one or more selected trucking companies that operate both the baseline and comparison configurations. The research will follow a study design developed in the research described in Problem Statement 1 and use data collection methods developed in the execution of Problem Statements 2 and 3. Exposure and data would be determined from company records. The study design would specify procedures for matching trips of baseline and comparison configurations control for route and driver characteristics. 7. Demonstrate evaluation procedures for trial programs to utilize specific larger and/or heavier truck combinations A comparative evaluation may be conducted by authorizing the use of specific larger and/or heavier trucks on a trial basis within specific jurisdictions and with mandatory evaluation. Evaluation of a trial operation of any specific truck configuration, in comparison to a baseline configuration, can be conducted with any of the three comparative evaluation methods described in Problem Statements 4, 5, and 6. 8. Establish protocols for the use of simulation modeling and test track evaluations to estimate safety performance of specific truck configurations Indirect methods, such as simulation modeling and test track evaluations, constitute the only feasible methods to anticipate the safety performance of truck configurations that are not in legal operation in any state. The research will establish protocols for simulation modeling of specific truck configurations, including model selection, maneuvers to be simulated, and performance measures. It will also establish protocols for test track evaluations, including the types of maneuvers to be evaluated, performance measures, and test procedures. Finally, the research will apply the protocols to truck configurations that already operate on U.S. roads, using either new data or existing data, and determine how effective the protocols are in estimating the known safety performance of those truck configurations. ===========================================================================
20 =========================================================================== BOX 9 Candidate Research Problem Statement Topics: Safety Consequences of Size and Weight Limit Changes Part 2: Long-Term Monitoring Programs for Evaluation of the Safety Performance of Truck Configurations Long-term monitoring programs would continuously monitor the safety performance of specific truck configurations throughout an entire jurisdiction. The Fatality Analysis Reporting System (FARS) program, in which the National Highway Transportation Safety Administration pays states to gather extensive supplementary data on every fatal crash, might be a model on which long-term monitoring programs could be based. 1. Develop study designs for evaluations with large-scale monitoring data This research will develop study designs for comparative evaluations using continuous monitoring data in order to direct the research described in Problem Statements 2â6. 2. Demonstrate statewide implementation of crash data enhancement procedures By the time this research is undertaken, crash data enhancement procedures will have been tested in the research of Problem Statement 2 in Box 8 and may have been implemented in research in Problem Statements 4, 5, and 6 in Box 8. This research applies the crash data enhancement procedures on a statewide scale in one or more states. The research will include the demonstration of necessary administrative arrangements among agencies for data collection. 3. Demonstrate statewide implementation of truck weight and configuration exposure estimation procedures This research will apply the exposure data enhancement procedures tested in the research of Problem Statement 3 in Box 8 on a statewide scale in one or more states. . 4. Demonstrate large scale use of trucking company data for monitoring This research will assemble crash and exposure data from trucking companies with proprietary information removed. The research may involve the creation of databases that can be used in conjunction with public agency data for specific studies under conditions agreed to with the owners of the data or the creation of public-facing databases that can be used by any researcher. 5. Demonstrate integration of large-scale monitoring data with existing data systems Effective evaluation studies with the data developed from execution of Problem Statements 2, 3, and 4 will require that the new data be integrated with traditional crash and exposure databases. This research will address procedures for accomplishing that integration. 6. Implement monitoring and conduct comparative evaluations of the safety performance of truck configurations using large-scale monitoring data This research will implement the monitoring systems demonstrated in the research in Problem Statements 2â5 and use the data to execute the study designs developed in Problem Statement 1. The studies will estimate the comparative safety performance of baseline trucks and specific larger or heavier trucks. The first evaluations would be one-time evaluations with larger sample sizes than would be possible in the targeted evaluations. However, because the data are to be collected on a continuing basis, evaluations also could be conducted on a continuing basis. ===========================================================================
21 Enforcement Research Evaluation of changes in truck size and weight limits may require assessing the enforcement of truck size, weight, and safety regulations from three perspectives. First, changes in the limits may affect the costs and methods of enforcement agencies. If costs increase or enforcement becomes more complex, then the impact of the change in limits will depend on enforcement agenciesâ ability to maintain effort. Second, pavement and bridge costs of changes in limits cannot be predicted confidently if the shares of present costs attributable to legal and illegal overloads are unknown. The 2002 TRB committee that reviewed past truck size and weight studies concluded that monitoring of compliance with weight regulations is too unsystematic to allow the costs of noncompliance to be estimated (TRB 2002, 5). Since that study, more data have become available from weigh-in-motion installations, but analyses of overweight frequency and associated bridge and pavement costs are not commonly carried out. Finally, changes in enforcement practices may be a means of mitigating infrastructure and safety costs of changes in limits. Identifying appropriate enforcement methods to accompany changes in limits would be a component of a truck size and weight study that adopted a systems perspective and sought the best combination of regulations, enforcement methods, infrastructure management, and user fees. Candidate enforcement research problem statement topics identified by the committee (see Box 10) would provide methods for these assessments. Research to understand the relationship between weight enforcement effort and the frequency of weight violations would be valuable for planning and budgeting enforcement programs, regardless of whether truck size and weight limits are changed.
22 =========================================================================== BOX 10 Candidate Research Problem Statement Topics: Enforcement and Compliance Implications of Changes in Truck Size and Weight Limits 1. Measure relationships between enforcement level of effort and frequency of violations for enforcement of truck size and weight regulations, as well as truck safety regulations. The research would include the definition and evaluation of alternative measures of effort and effectiveness and would distinguish relative effectiveness of alternative methods and strategies of enforcement. 2. Develop estimates of enforcement agenciesâ costs for the enforcement of truck size, weight, and safety regulations. Cost data would separate weight and safety enforcement costs. Cost relationships would be developed to support projections of the change in the cost of enforcement activities necessitated by changes in truck size and weight limits. 3. Conduct a survey and a synthesis of the methods of enforcing truck size and weight limits and standards and monitoring compliance in other countries with diverse combination vehicle populations, including Australia, Canada, and the European Union. The survey should cover the enforcement of requirements that differ according to the dimensions of the vehicles. It should obtain information on enforcement and monitoring intensity, use of information technology in enforcement, and measures of enforcement effectiveness. 4. Design and conduct pilot studies to evaluate emerging technologies to automate enforcement and to improve compliance with truck size and weight regulations. =========================================================================== Mode Choice and Freight Market Research Estimates of the aggregate impacts of changing truck size and weight limits depend on underlying projections of how shippers and carriers would respond to the new regulations. Safety impacts will depend on the change in the volume and distribution of truck traffic, as well as on the relative safety performance of new truck configurations. Aggregate infrastructure costs related to the cumulative impact of traffic will depend on the change in truck traffic volume and on the change in the distribution of axle weights. Candidate problem statement topics for research to improve freight market analysis capabilities are listed in Box 11.
23 =========================================================================== BOX 11 Candidate Research Problem Statement Topics: Effect of Changes in Truck Size and Weight Limits on Freight Costs, Mode Shares, and Truck Traffic Volume 1. Conduct qualitative research aimed at understanding how shippers, carriers, and receivers make decisions regarding vehicle and mode choices suitable for their operations. This could be a combination of in-depth interviews, focus groups, and other forms of qualitative research. 2. Develop a suite of freight market models capable of estimating the effect of changes in truck size and weight regulations on truck traffic. The models should also be capable of estimating the effect on truck traffic of changes in highway user fees that aligned fees with highway agency infrastructure costs attributable to trucks of various dimensions. The research will include developing, testing, and comparing alternative modeling techniques, including disaggregate methods, econometric models, and aggregate techniques that seek to estimate the market shares for each of the vehicle and freight modes as a function of the average characteristics of the competing vehicle and modes. The research may include refinement of USDOTâs Intermodal Transportation and Inventory Costing (ITIC) model to better reflect real-world mode choice decisions. 3. Develop models of the effects of changes in truck costs on the volume of truck traffic in the long run. Changes in truck size and weight limits that reduce truck transportation costs may affect truck traffic volume by influencing shippersâ decisions regarding shipment size and frequency, location of production and distribution facilities, sources of production inputs, and market destinations of products. Some of these effects will be apparent only after several years. 4. Develop network models capable of estimating the effect of vehicle and mode choice changes on a multi-model network. Models will be needed to estimate the impact on truck use of route closings caused by the posting of weight restrictions on inadequate bridges and to estimate the effect of truck size and weight limit changes on traffic on short line and Class I railroads. 5. Resume conducting the Vehicle Inventory and Use Survey (VIUS) as a source of systematic data on truck shipment sizes, truck cargo capacities, and the truck configurations and body types suitable for carrying specific commodities. 6. Conduct qualitative research to identify the possible consequences of electrification of commercial trucks relevant to the evaluation of truck size and weight limits. For example, such consequences might include changes in the capital and operating costs of trucks and changes in the benefits of added weight and volume capacity that would influence vehicle choice and mode choice. ========================================================================== Research on Methods to Evaluate Truck Size and Weight Regulatory and Management Options The infrastructure and safety models produced by the research outlined above would predict the impacts of operating specified vehicles on specified roads. Past truck size and weight studies (including the TRB 1990 and 2002 studies and the USDOT 1981 and 2000 studies) were not limited to such engineering analyses. Rather, they evaluated scenarios defined as practical regulatory schemes. For example, changes
24 in regulations may involve route restrictions, permit requirements, or special fees in addition to changes in the size and weight limits. Changes in federal regulations may be preemptive (overriding conflicting state regulation) or permissive (allowing states to choose whether to adopt new limits). Estimates of costs and benefits will depend on these features of the regulations. Cost and benefit estimates will also depend on assumptions about how state and local government highway agencies and enforcement agencies will adjust their activities in response to changes in the characteristics of truck traffic. A truck size and weight policy study should be structured to clearly and objectively present trade-offs, risks, and uncertainties among the policy options considered. Candidate problem statements for research to provide the capability to evaluate these aspects of truck size and weight regulations are listed in Box 12. =========================================================================== BOX 12 Candidate Research Problem Statement Topics: Methods to Evaluate Truck Size and Weight Regulatory and Management Options 1. Develop methods for incorporating common features of regulatory schemes in evaluations of costs and benefits of changing truck size and weight limits. These features include road network restrictions, permissive versus preemptive federal regulations, permit requirements for vehicles exceeding certain limits, performance standards for vehicle stability and control, user fees related to infrastructure costs imposed by specific truck operations, and grandfather and/or other special exemptions from limits. 2. Develop an analysis framework for evaluating the potential of the coordination of size and weight regulations with other road management policies to increase public benefits from the road system. The policies to be coordinated would include user fees, the enforcement of truck regulations, road and bridge design, and asset management. 3. Develop and test methods for systematically assessing uncertainty in truck size and weight studies and for presenting that uncertainty in a format useful to decision makers. The methods must be able to express uncertainties arising simultaneously from multiple sources. Demonstrate the application of methods for guiding regulatory decisions when outcomes are uncertain that have been developed in other fields (e.g., environmental regulation) to truck size and weight regulation. 4. Develop protocols for conducting staged pilot evaluations of truck configurations. ===========================================================================