Comprehensive Truck Size and Weight Limits Study: Linkage between the Revised Desk Scans and Project Plans Report
Chapter 3: Compliance Comparative Analysis
3.1 Purpose
The purpose of this section is to document how the information and understanding gained through the Desk Scan informed the technical methodology undertaken in the Compliance Comparative Analysis. The technical methodology was initially provided in the Project Plan and subsequently revised throughout the course of the project as details about available data emerged and analytical approaches were refined. As such, the linkages in this report reference the Project Plan as manifested in the Compliance Comparative Analysis technical report. The original Project Plan has not been revised.
This report establishes linkages in two principal areas:
- Linkages regarding the general technical approach: The report establishes the linkage between literature findings on approaches to analyze enforcement costs and effectiveness with the development and application of the performance-based approach applied in the 2014 CTSW Study.
- Linkages regarding available data/analysis methods: Based on the assessment of research and data needs summarized in the revised Desk Scan, this report links literature findings with the use and integration of the data sources used in the 2014 CTSW Study. Details are also provided about linkages concerning the more detailed aspects of the technical approach (e.g.,the use of state-level and vehicle-specific comparisons).
3.2 Linkages Regarding the General Technical Approach
This section describes the linkage between the general technical approach applied in the Compliance Comparative Analysis and the approaches used and/or recommended in the literature. Portions of the text are excerpted directly from the Compliance Comparative Analysis technical report and the revised Desk Scan.
3.2.1 Summary Description of the 2014 CTSW Study's Technical Approach
The analysis of the costs and effectiveness truck size and weight (TSW) enforcement programs undertaken in the Compliance Comparative Analysis applies a performance-based approach. This approach considers enforcement program performance (or effectiveness) in terms of inputs, outputs, outcomes, and pertinent relationships between these measures. Effective enforcement of TSW limits is critical to the realization of regulatory compliance (i.e., the primary performance outcome of an enforcement program) and its impacts on safety, infrastructure, and industry competitiveness (Organisation for Economic Co-operation and Development (OECD) 2011; U.S. Department of Transportation 2000 (USDOT); Transportation Research Board (TRB) 1990).
Enforcement program inputs reflect the resources available to carry out the TSW enforcement task. As shown in Table 3-1, the measures of input included in the Compliance Comparative Analysis are program cost (disaggregated into costs for personnel and facilities) and the number and type of weigh scales used to enforce truck weights, including weigh-in-motion (WIM) sites used for screening truck weights.
Outputs reflect the way enforcement resources are used, the scale or scope of activities performed, and the efficiency of converting allocated resources into a product. Outputs help answer the question: what will/did we do with the resources given to us? As shown in Table 3-1, the measures of output used in the Compliance Comparative Analysis are the number of weighings, number of citations, number of vehicles required to shift loads or offload cargo to achieve compliance, and the number of permits issued for oversize/overweight (OS/OW) loads. While these outputs on their own provide some indication of program effectiveness, effectiveness can be further understood by relating certain program outputs and inputs. Three pertinent relationships are established, namely: the weighing cost-efficiency (weighings per personnel cost), the citation rate (citations per weighing), and the relationship between citation rate and enforcement intensity (measured as the number of weighings per truck vehicle-miles of travel).
Outcomes reflect the degree of success of the TSW enforcement program in achieving its goals and objectives. Outcomes help answer the question: what will/did we achieve in relation to our purpose? From an operational and programmatic perspective, the goal of enforcement is to achieve compliance with TSW regulations. Success in achieving compliance ultimately improves safety, mitigates infrastructure deterioration, and promotes fairness and competitiveness within the trucking industry. As shown in Table 3-1, the outcome measures used in the Compliance Comparative Analysis are the proportion of underweight axle or truck observations and the severity of overweight observations.
| Type of Measure | Performance Measures |
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| Input |
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| Output |
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| Outcome |
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The distinction between outputs and outcomes, while subtle, is important because measuring outputs may encourage efforts to increase certain output measures (e.g., the number of citations observed or reported), which should in fact decrease if enforcement achieves its overall goal of better compliance. In contrast, outcome-oriented measures may describe the proportion of compliant events (which may suggest successful enforcement) or the severity of overweight observations (which may suggest a lack of enforcement success). Conventional evaluations of enforcement programs have relied on outputs more than outcomes, presumably because outputs are easier to measure and monitor over time.
3.2.2 Justification for the 2014 CTSW Study's Technical Approach
The performance-based approach has been widely recommended by recent research and development concerning TSW enforcement programs at the state and national levels. This approach enabled a systematic analysis of the performance-in terms of cost and effectiveness-of TSW enforcement from a programmatic perspective. Principal examples of relevant literature on this topic are summarized briefly below (the revised Desk Scan contains additional details about each of these documents):
- Hanscom (1998) recognizes the need to develop performance measures to support better analysis and understanding of the costs and effectiveness of enforcement programs. The research develops performance measures for truck weight enforcement activities. The focus of the research is to identify quantifiable measures that reflect the goals of an enforcement program rather than using traditional indicators such as the number of trucks weighed, the number of violators detected, or the amount of fines collected. The measures proposed in this report provided the basis for the selection of the performance measures used in the 2014 CTSW Study (see Table 3-1).
- URS (2005) describes what a performance-based approach to enforcement would involve and makes the distinction between inputs, outputs, and outcomes (i.e., performance). These distinctions are generally consistent with those discussed above for the 2014 CTSW Study. Many of the performance measures proposed by URS are similar to those identified by Hanscom (1998). A more recent report by URS (2013), also recommends the development of an outcome-driven truck weight compliance program.
- Fekpe et al. (2006) encourage the use of a performance-based compliance program and describe how this type of program may be designed and applied, particularly in the context of OS/OW permitting. The authors indicate that a performance-based program should be robust and simple to administer, implement, and monitor, and should use performance measures (or surrogate measures) that are easy to obtain using simple and quick roadside tests. They acknowledge that this may require an approach that differentiates trucks by configuration, commodity, and highway type in terms of enforcement and data collection. The 2014 CTSW Study particularly requires differentiation of performance measures by truck configuration.
- DalPonte et al. (2015) evaluate the performance measures used in Oregon's truck weight enforcement program and suggest how Oregon's approach may improve federal oversight of states' enforcement programs. Some of the measures and relationships among the measures are consistent with those used in the 2014 CTSW Study.
The performance-based approach applied in the Compliance Comparative Analysis extends the scope of analysis undertaken at the federal level concerning TSW enforcement programs beyond what was considered in the previous USDOT 2000 CTSW Study, but also maintains a general consistency in the type of analysis performed (see USDOT 2000). As in the 2014 CTSW Study, the 2000 CTSW Study provided national-level statistics concerning enforcement program costs (for one year) and a number of enforcement program outputs (e.g., weighings, citations, and citation rate). To support the objectives of the 2014 CTSW Study, these measures are also examined at a state-specific level and new measures are introduced (e.g., weighing cost-efficiency, citation rate as a function of enforcement intensity). Moreover, the costs and effectiveness of enforcing truck weights for specific vehicle configurations are investigated through a scenario analysis.
3.3 Linkages Regarding Available Data/Analysis Methods
This section describes linkages between the data/analysis methods used in the Compliance Comparative Analysis and the data/analysis methods discussed in the literature. Portions of the text are excerpted directly from the Compliance Comparative Analysis technical report and the revised Desk Scan.
3.3.1 Summary Description of the Data/Analysis Methods Used in the CTSW Study
Application of the performance-based approach provides the supporting framework for a comparative analysis designed to reveal insights about the costs and effectiveness of TSW enforcement programs. Data limitations, consistency, and availability constrain a comprehensive, representative understanding of enforcement costs and effectiveness (Transportation Research Board 2002; Carson 2011), particularly for specific vehicle configurations. Therefore, the Compliance Comparative Analysis integrates three primary data sources to support a multi-faceted analysis of truck weight enforcement costs and effectiveness at the national-level, using state-level comparisons, and through vehicle-specific comparisons within the scenario analysis. These three data sources are: (1) federal data on enforcement costs and activities; (2) WIM data; and (3) experiential data.
3.3.1.1 Federal Data on Enforcement Costs and Activities
State Enforcement Plans (SEPs) submitted annually by states to the FHWA provide the primary source data for the analysis of enforcement costs and resources (i.e., program inputs). Tabulated summaries for key input measures from 2008 to 2012 are analyzed (i.e., total costs, facilities costs, personnel costs, quantity of weigh scale equipment). The data enable state-level comparisons of enforcement program costs; however, the SEPs do not contain any systematically reported information about TSW enforcement costs for specific vehicle configurations, routes, networks, industries, commodities, or permitted versus non-permitted trucks.
The Annual Certifications of Truck Size and Weight Enforcement database provides the primary source data for the analysis of key enforcement program output measures (i.e., weighings, citations, load shifting and off-loading requirements, permit issuance activities, and output-based relationships). Data from 2008 to 2012 are included in the analysis. As with the SEP data, this database enables state-level comparisons but precludes any disaggregation of enforcement activity for specific vehicle configurations. Moreover, citation data cannot be linked to the enforcement method (e.g., fixed weighing, portable weighing, semi-portable weighing) used to obtain the citation.
3.3.1.2 WIM Data
WIM data from selected locations are used to assess truck weight compliance outcomes (in terms of the proportion of underweight observations and the severity of overweight observations) at a vehicle-specific level. Comparing the distributions of axle and gross vehicle loads with static weight limits enables the assessment of truck weight compliance for certain control and alternative truck configurations. WIM devices measure the axle weights (and by summing these, the gross vehicle weight), the spacing of these axles, and speed of a passing vehicle without requiring the vehicle to stop.
While WIM data enable a vehicle-specific analysis of weight compliance, they are subject two limitations (among others). First, properly installed and calibrated WIM devices are subject to measurement errors, which vary in magnitude depending on the type of equipment used. Second, many factors influence the axle weights recorded by a WIM device. For example, the intensity of enforcement present, the weight limits on proximal highway networks, the industries operating in the region, and the proportion of permitted trucks in the traffic stream all influence weight measurements. The effects of these factors are generally unquantifiable.
3.3.1.3 Experiential Data
Experiential data, gained from the insights of commercial motor vehicle state enforcement officials, are integrated into the Compliance Comparative Analysis. These insights pertain mainly to: (1) the designation of "federal" and "non-federal" states; and (2) weighing times for various truck configurations using common types of weigh scales. The integration of these insights helps fill data gaps in the analysis and ensure that the analysis findings are grounded in the practical realities of on-road truck weight enforcement.
3.3.2 Justification for the Data/Analysis Methods Used in the 2014 CTSW Study
The application of each of the three foregoing data/analysis methods within the context of TSW enforcement programs has been addressed in the literature, as summarized below.
3.3.2.1 Federal Data on Enforcement Costs and Activities
Literature published in the early-1990s recommends continued development of a national-level data program to support evaluations of states' TSW enforcement programs (TRB 1990; Office of Inspector General 1991). By 2000, the USDOT notes a general improvement in the level of enforcement activity resulting from requirements for states to develop and certify state enforcement plans (SEPs) and the adoption of technologies such as WIMs for pre-screening. This state-submitted data has been used to track enforcement costs and effectiveness, principally in terms of the number of trucks weighed, the number of citations issued, violation rates, and requirements for vehicle offloading and load shifting (USDOT 2000).
The 2014 CTSW Study provides a national-level analysis of TSW enforcement program costs and effectiveness, similar to the analysis conducted as part of the 2000 CTSW Study. However, the current 2014 CTSW Study also disaggregates the data to support state-level comparisons.
3.3.2.2 WIM Data
The use of WIM data to assess truck weight compliance has been evident in the literature for several decades, albeit with some notable limitations. Principal references on this topic follow (the revised Desk Scan contains additional details about each of these documents):
- TRB (2002) cites recommendations made in the 1991 Office of Inspector General report which identifies the need to develop standards and technological improvements for WIM systems.
- URS (2005) identifies WIM devices as a data source for the calculation of TSW enforcement program performance measures.
- Regehr et al. (2010) use WIM data to assess truck weight regulatory compliance for three long truck configurations (Rocky Mountain doubles, Turnpike doubles, and triple trailer combinations) operating under special permit in the Canadian Prairie Region. The authors do not attempt to link their results to on-road enforcement methods.
- The OECD (2011) recognizes the value of applying WIM to support truck weight enforcement programs. This report states that WIM technologies have the potential to deliver more detailed, continuous data about weight compliance, specifically by utilizing axle spacing measurements to isolate the compliance record of higher capacity configurations.
The 2014 CTSW Study utilizes available WIM data to assess truck weight compliance for the control vehicles and alternative configurations specified for the scenario analyses. The limitations and assumptions of applying WIM data for this purpose are noted.
3.3.2.3 Experiential Data
The integration of experiential data into the more empirical analyses conducted in the 2014 CTSW Study is an approach supported by the literature, particularly where known data gaps exist. The revised Desk Scan references several reports that utilize industry surveys to develop an understanding of the performance of TSW enforcement programs. Four recent reports are particularly noteworthy (the revised Desk Scan contains additional details about each of these documents):
- Straus and Semmens (2006) estimate the cost of overweight vehicle travel on Arizona highways. To support this work, the authors provide results from a survey of 25 states concerning their experiences with truck weight enforcement and overweight trucking.
- Honefanger et al. (2007) summarize and evaluate procedures and technologies for enforcing TSW laws in Europe (Belgium, France, Germany, the Netherlands, Slovenia, and Switzerland), based on an international scanning tour which involved interviews with TSW enforcement officials from each of these countries.
- Ramseyer et al. (2008) report findings from a state-based survey of TSW enforcement officials which provides useful information about truck weights and overloading.
- Cambridge Systematics (2009) interviews nine states to determine best practices in the deployment of roadside enforcement technologies.
3.4 References
Cambridge Systematics.
-2009. Truck Size and Weight Enforcement Technologies - Implementation Plan. Washington D.C.: Federal Highway Administration.
Carson, J.
-2011. Directory of Significant Truck Size and Weight Research. Washington, D.C.: American Association of State Highway and Transportation Officials.
DalPonte, G., Fortey, N., & Scrivner, E.
-2015. "Using Performance Measures to Lighten the Load-Re-thinking the Size and Weight Enforcement Program" Transportation Research Board Annual Meeting. Washington, D.C.: Transportation Research Board.
Fekpe, E., Gopalakrishna, D., & Woodrooffe, J.
-2006. "Conceptual Framework for a Performance-Based Oversize and Overweight Permitting System." International Symposium on Heavy Vehicle Weights and Dimensions - HVWD9. State College, PA: International Forum for Road Transport Technology.
Hanscom, F.
-1998. Developing Measures of Effectiveness for Truck Weight Enforcement Activities. Washington, D.C.: National Cooperative Highway Research Program.
Regehr, J.D., Montufar, J., Sweatman, P., & Clayton, A.
-2010. "Using exposure-based evidence to assess regulatory compliance with productivity-permitted long trucks." 11th International Symposium on Heavy Vehicle Transport Technology. Melbourne, Australia: International Federation of Road Transport Technology.
Office of Inspector General.
-1991. Report on the Audit of the Vehicle Weight Enforcement Program. Washington, D.C.: U.S. Department of Transportation.
Organisation for Economic Co-operation and Development and the International Transport Forum.
-2011. Moving Freight with Better Trucks. Paris: Organisation for Economic Co-operation and Development.
Transportation Research Board.
-2002. Regulation of Weights, Lengths, and Widths of Commercial Motor Vehicles. Washington,
D.C.: Transportation Research Board.
-1990. Truck Weight Limits: Issues and Options. Washington, D.C.: Transportation Research Board, National Research Council.
United States Department of Transportation.
-2000. Comprehensive Truck Size and Weight Study. Washington, D.C.: United States Department of Transportation.
URS.
-2005. Minnesota Statewide Commercial Vehicle Weight Compliance Strategic Plan. Minneapolis, MN: Minnesota Department of Transportation.
-2013. Indiana Truck Weight Compliance Business Plan. Unpublished: Indiana Department of Transportation, Indiana State Police, and Indiana Department of Revenue.
