Comprehensive Truck Size and Weight Limits Study - Compliance Comparative Analysis Technical Report
Chapter 1: Introduction
1.1 Background
MAP-21 directs the Secretary of Transportation, in consultation with State and other Federal agencies, to conduct a series of analyses assessing the impacts from trucks operating at or within current Federal size and weight regulations as compared to the impacts from trucks operating above those limits with a particular focus on impacts to:
- Highway safety and truck crash rates;
- Infrastructure (pavement) service life;
- Highway bridge performance; and
- Delivery of effective enforcement programs.
The United Stated Department of Transportation (USDOT), in conjunction with a group of independent stakeholders, identified six different vehicle configuration scenarios, each involving one of the alternative truck configurations, to assess the likely results of allowing widespread alternative truck configurations to operate on different highway networks.
The results of this 2014 Comprehensive Truck Size and Weight Limits Study (2014 CTSW Study) study are presented in a series of technical reports. These include:
- Volume I: Comprehensive Truck Size and Weight Limits Study – Technical Summary Report. This document gives an overview of the legislation and the study project itself, provides background on the scenarios selected, explains the scope and general methodology used to obtain the results, and gives a summary of the findings.
- Volume II: Comprehensive Truck Size and Weight Limits Study. This volume comprises a set of five comparative assessment documents that meet the technical requirements of the legislation:
- Modal Shift Comparative Analysis,
- Pavement Comparative Analysis,
- Highway Safety and Truck Crash Comparative Analysis,
- Compliance Comparative Analysis
- Bridge Structure Comparative Analysis
The Volume II: Compliance Comparative Analysis presents the analysis of the six alternative truck size and weight configurations (scenarios) selected for study and describes in detail the approach, data, models, limitations, and assumptions underlying estimates of potential compliance impacts associated with the six scenarios.
1.2 Purpose
Meaningful control of truck size and weight (TSW) requires the enforcement of relevant laws and regulations. Effective enforcement programs seek to efficiently allocate resources and technological investments in a manner which achieves regulatory compliance, and ultimately improves safety, protects highway infrastructure, and promotes fairness within the road transport industry.
This report documents the results from the Volume II: Compliance Comparative Analysis, a component of the USDOT 2014 Comprehensive Truck Size and Weight Limits Study (2014 CTSW Study). The purpose of this study is to assess the cost and effectiveness of enforcing TSW limits for trucks operating at or below current Federal truck weight limits as compared with enforcement costs and effectiveness for alternative truck configurations in six scenarios. The results of the comparative analyses of enforcement cost and effectiveness are reported in Chapter 2 and Chapter 3 of this report, respectively.
Enforcement costs reflect the resources required to undertake the TSW enforcement task. The cost analysis includes a description of the principal TSW enforcement methods used in the United States, including the application and costs of enforcement technologies. The analysis examines national-level trends in enforcement program costs and conducts enforcement cost comparisons between States and for different truck configurations. Finally, the analysis estimates the enforcement cost impacts of introducing the alternative truck configurations into the traffic stream.
Enforcement program effectiveness reflects how the resources provided to the enforcement program translate into TSW enforcement actions and ultimately contribute to achieving regulatory compliance. The effectiveness analysis examines trends and relationships pertaining to enforcement program activities (such as truck weighings) and compares effectiveness between States and for different truck configurations. Weigh-in-motion (WIM) data gathered at selected sites provides the basis for comparing the truck weight compliance impacts that may result from introducing the alternative truck configurations into the traffic stream.
1.3 Context and Approach
Effective enforcement of TSW limits is critical to the realization of regulatory compliance and its impacts on safety, infrastructure, and industry competitiveness (Organization for Economic Cooperation and Development (OECD) 2011; U.S. Department of Transportation 2000; Transportation Research Board (TRB) 1990). However, despite the widely held notion of a linkage between truck weight enforcement and compliance, there remains an inability to fully understand this relationship because of differences in how enforcement occurs and a lack of systematic and reliable evidence concerning overweight trucking (Carson 2011). Additionally, understanding this relationship for specific truck configurations—one of the main issues of interest in this 2014 CTSW Study—has generally been constrained by insufficient data.
Increasing investments in proven enforcement technologies, including tools for identifying non-compliant trucks or carriers and the expanded use of WIM devices for monitoring truck weights, provide some opportunity to address these historical data limitations (OECD 2011; Cambridge Systematics 2009); however, certain data gaps persist, precluding a definitive analysis of the subject.
The analysis of costs and effectiveness undertaken in this study takes a performance-based approach. This approach considers enforcement program performance (or effectiveness) in terms of inputs, outputs, outcomes, and pertinent relationships between these measures. This performance-based approach extends the scope of analysis undertaken at the Federal level concerning TSW enforcement programs beyond what was considered in the previous 2000 Comprehensive Truck Size and Weight Study (2000 CTSW Study) (see USDOT 2000). More recent research and development for enforcement programs at the State and national levels has advanced this approach and shaped the analysis undertaken in this 2014 CTSW Study (URS 2013; Fekpe et al. 2006; URS 2005; Hanscom 1998).
Enforcement program inputs reflect the resources available to carry out the TSW enforcement task. As shown in Table 1, the measures of input included in this study are program cost (disaggregated into costs for personnel and facilities) and the number and type of weigh scales used to enforce truck weights, including 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 or did we do with the resources given to us? As shown in Table 1, the measures of output used in this Report 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 (VMT)).
Outcomes reflect the degree of success of the TSW enforcement program in achieving its goals and objectives. Outcomes help answer the question: what will or 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.
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.
Applying 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, particularly regarding vehicle-specific comparisons. To accommodate these limitations and leverage existing datasets and institutional knowledge, this study applies two types of comparisons.
First, at the broader level, readily available, State-specific data provides the foundation for comparing costs and effectiveness between States that currently allow trucks above Federal weight limits and those that do not. As the state-level data used in these comparisons do not allow disaggregation by vehicle configuration, these comparisons can reveal potential vehicle-specific differences at a State level. Because of budget constraints, a subset of 29 States (referred to as comparison States) are used for this analysis. Based on recommendations by FHWA, the American Association of Highway Transportation Officials (AASHTO) Subcommittee on Highway Transport (SCOHT), and representatives from the Commercial Vehicle Safety Alliance (CVSA), the 29 States were selected because they: (1) are considered to be enforcement programming leaders in the nation; (2) have experience in enforcing vehicles subject to grandfather[1] provisions (e.g., longer combination vehicles); or (3) have recently undertaken research and development projects related to TSW enforcement. In addition, the selection of these States considered the need to represent general variations in trucking operations across the Nation (e.g., configurations in use, industries served) and geographic factors.
Second, a more specific comparative analysis of enforcement program costs and effectiveness involves vehicle-specific comparisons (where possible). These comparisons focus on cost and effectiveness differences between the control vehicles and the six alternative truck configurations used in the six 2014 CTSW Study scenarios (Table 2). Thus, the results of the vehicle-specific comparisons directly support the scenario analysis, which estimates system-wide cost and effectiveness impacts that could result from the operation of the alternative truck configuration relative to the base case. In the cost analysis, the relevant performance measure is the cost of weighing the alternative truck configurations. In the effectiveness analysis, the relevant performance measures for assessing compliance are obtained for locations where representative data are available (principally WIM data). This assessment enables a quantitative analysis of certain compliance outcomes for the alternative truck configurations (such as the proportion of weight-compliant observations and the severity of overweight observations for specific truck configurations at that location). These compliance outcomes, however, cannot be directly related to enforcement activities to ascertain the effect of enforcement on these outcomes.
| Scenario | Configuration | Depiction of Vehicle | # Trailers or Semi-trailers | # Axles | Gross Vehicle Weight (pounds) |
Roadway Networks |
|---|---|---|---|---|---|---|
| Control Single | 5-axle vehicle tractor,53 foot semitrailer (3-S2) |  |
1 | 5 | 80,000 | STAA 1 vehicle; has broad mobility rights on entire Interstate System and National Network including a significant portion of the NHS |
| 1 | 5-axle vehicle tractor, 53 foot semitrailer (3-S2) |  |
1 | 5 | 88,000 | Same as Above |
| 2 | 6-axle vehicle tractor, 53 foot semitrailer (3-S3) |  |
1 | 6 | 91,000 | Same as Above |
| 3 | 6-axle vehicle tractor, 53 foot semitrailer (3-S3) |  |
1 | 6 | 97,000 | Same as Above |
| Control Double | Tractor plus two 28 or 28 ½ foot trailers (2-S1-2) |  |
2 | 5 | 80,000 maximum allowable weight 71,700 actual weight used for analysis 2 | Same as Above |
| 4 | Tractor plus twin 33 foot trailers (2-S1-2) |  |
2 | 5 | 80,000 | Same as Above |
| 5 | Tractor plus three 28 or 28 ½ foot trailers (2-S1-2-2) |  |
3 | 7 | 105,500 | 74,500 mile roadway system made up of the Interstate System, approved routes in 17 Western States allowing triples under ISTEA Freeze and certain four-lane PAS roads on East Coast 3 |
| 6 | Tractor plus three 28 or 28 ½ foot trailers (3-S2-2-2) |  |
3 | 9 | 129,000 | Same as Scenario 5 3 |
1 The STAA network is the National Network (NN) for the 3S-2 semitrailer (53 feet) with an 80,000-lb. maximum GVW and the 2-S1-2 semitrailer/trailer (28.5 feet) also with an 80,000 lbs. maximum GVW vehicles. The alternative truck configurations have the same access off the network as its control vehicle. Return to Table Note 1
2 The 80,000 pound weight reflects the applicable Federal gross vehicle weight limit; a 71,700 gross vehicle weight was used in the study based on empirical findings generated through an inspection of the weigh-in-motion data used in the study. Return to Table Note 2
3 The triple network is 74,454 miles, which includes the Interstate System, current Western States’ triple network, and some four-lane highways (non-Interstate System) in the East. This network starts with the 2000 CTSW Study Triple Network and overlays the 2004 Western Uniformity Scenario Analysis, Triple Network in the Western States. There had been substantial stakeholder input on networks used in these previous USDOT studies and use of those provides a degree of consistency with the earlier studies. The triple configurations would have very limited access off this 74,454 mile network to reach terminals that are immediately adjacent to the triple network. It is assumed that the triple configurations would be used in LTL line-haul operations (terminal to terminal). The triple configurations would not have the same off network access as its control vehicle–2S-1-2, semitrailer/trailer (28.5 feet), 80,000 lbs. GVW. The 74,454 mile triple network includes: 23,993 mile network in the Western States (per the 2004 Western Uniformity Scenario Analysis, Triple Network), 50,461 miles in the Eastern States, and mileage in Western States that was not on the 2004 Western Uniformity Scenario Analysis, Triple Network but was in the 2000 CTSW Study, Triple Network (per the 2000 CTSW Study, Triple Network). Return to Table Note 3
1.4 References
Cambridge Systematics, Truck Size and Weight Enforcement Technologies - State of the Practice, Washington D.C.: Federal Highway Administration, 2009(a).
Carson, J. (2011). Directory of Significant Truck Size and Weight Research, Washington, D.C.: American Association of State Highway and Transportation Officials.
Fekpe, E., Gopalakrishna, D., & Woodrooffe, J., “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, 2006.
Hanscom, F., Developing Measures of Effectiveness for Truck Weight Enforcement Activities, Washington, D.C.: National Cooperative Highway Research Program, 1998.
Organisation for Economic Co-operation and Development and the International Transport Forum, Moving Freight with Better Trucks, Paris: Organisation for Economic Co-operation and Development, 2011.
Transportation Research Board, Special Report 225: Truck Weight Limits: Issues and Options, Washington, D.C.: National Research Council, 1990.
United States Department of Transportation, Comprehensive Truck Size and Weight Study. Washington, D.C.: USDOT, 2000.
URS, Indiana Truck Weight Compliance Business Plan, Unpublished: Indiana Department of Transportation, Indiana State Police, and Indiana Department of Revenue, 2013.
Minnesota Department of Transportation, Minnesota Statewide Commercial Vehicle Weight Compliance Strategic Plan. Minneapolis, MN: MNDOT, 2005).
[1] The Federal government began regulating truck size and weight in 1956 when the National Interstate and Defense Highways Act (Public Law 84-627), establishing the Interstate Highway System, was enacted. A state wishing to allow trucks with sizes and weights greater than the Federal limits was permitted to establish "grandfather" rights by submitting requests for exemption to the FHWA. During the 1960s and 1970s, most grandfather issues related to interpreting State laws in effect in 1956 were addressed, and so most grandfather rights have been in place for many decades. See USDOT Comprehensive Truck Size and Weight Study, Volume 2, "Chapter 2: Truck Size and Weight Limits Evolution and Context," FHWA-PL-00-029 (Washington, DC: FHWA, 2000), p. II-9. Return to Footnote 1
