Regulation of Weights, Lengths, and Widths of Commercial Motor Vehicles Special Report 267 (2002) / Chapter Skim
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4. Mitigation
4. Mitigation
Pages 154-188
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From page 154... ...
It is limited to three categories of measures that are closely linked to size and weight issues: · Changes made in vehicle design to reduce accident risk or highway infrastructure wear Size and weight policy proposals, including those of past TRB studies, often have included recommendations that changes in size and weight limits be accompanied by vehicle design requirements intended to offset potentially harmful consequences of the changes. The rules of state overweight permit programs sometimes incorporate such requirements.
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From page 155... ...
Evaluation of changes in size and weight regulations should include consideration of the practicality of enforcing the new rules. Certain mitigation actions not discussed in this chapter are described in Chapters 2 and 3: · More intensive bridge management, inspection, and maintenance as an alternative to bridge posting or replacement to accommodate heavier loads; · Construction of heavier, more durable pavements, which conceivably could reduce the total cost of truck traffic; and · Close matching of highway user fees to the costs caused by each user, a potentially highly effective means of controlling costs by giving truck owners economic incentives to manage their operations in ways that reduce costs to the highway agency and other road users.
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From page 156... ...
The vehicle identification technology described later in this chapter would provide some of the capabilities needed to manage such a regulatory system. Vehicle design improvements, separation of car and truck traffic, and enforcement as means of mitigating the impacts of truck traffic are addressed in the first three sections below.
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From page 157... ...
That is, issuance of the vehicle permits recommended in the study would be used as an incentive to induce carriers to adopt safer practices: "The states should use the permit process to aggressively promote safety by establishing restrictions and by revoking the permits of carriers with serious or repeated safety violations." The Truck Weight Limits study committee recommended that standards be imposed on permit vehicle designs regarding power requirements for acceleration and hill climbing, brakes, connecting equipment between the tractor and semitrailer and between the two trailing units in a double-trailer configuration, axle width, and tires and rims. It also 157
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From page 158... ...
The intended effect of the B-train weight limit recommendation is to promote use of this vehicle design and consequently to mit158
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From page 159... ...
, the points at the vertices of the triangle plot the load transfer ratio (a safety performance measure) on the vertical axis with respect to gross weight (a productivity performance measure)
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From page 160... ...
A similar performance standards framework has been put forth as the basis for international harmonization of size and weight regulations under NAFTA (LTSS 1999~. A minimum allowable rollover threshold regulation was recently proposed by the government in New Zealand (Land Transport Safety Authority 2001)
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From page 161... ...
If the safety gains of a low loac! transfer ratio are large, the truck with lower gross weight anc!
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From page 162... ...
and 90,000 Ib maximum gross weight. The vehicle is reported by the manufacturer to have improved rollover resistance and an electronic suspension control feature that gives it acceptable cornering maneuverability during low-speed turns in spite of its trailer length (Moore 1998~.
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From page 163... ...
An important distinction, however, is that the pilot studies described in Chapter 3 would constitute a formal, established element of a regulatory process. That is, states, carriers, or others seeking federal authorization of the use of new vehicles or of other changes in size and weight regulations could instigate pilot studies under the control of the Commercial Traffic Effects Institute described in Chapter 3.
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From page 164... ...
The Rollover Stability Advisor system senses when the lateral acceleration of the vehicle is approaching the vehicle's rollover threshold and issues a warning to the driver (Winkler 2000, 14~. The Rollover Stability Controller system extends this capability by automatically intervening to slow engine speed when the threshold is approached.
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From page 165... ...
The program's focuses have included cab design, engine durability, and brake performance (Whitten 2001~. Mitigation of Highway Costs Through Vehicle Design Truck design improvements can reduce infrastructure costs as well as safety hazards.
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From page 166... ...
The TRB Turner Proposal study estimates that improved suspensions could reduce the cost of pavement wear by about 5 percent (TRB 199Ob, 176~. The maximum gross weight allowances for road-friendly suspensions recently enacted in Australia range from 3 to 9 percent for combination vehicles with five or more axles, suggesting that authorities there may be expecting a reduction in pavement wear somewhat greater than that estimated in the TRB study (NRTC no...
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From page 167... ...
Therefore, separation of cars and trucks might mitigate the impacts of truck traffic by reducing accident losses, congestion, and nuisance to car travelers. Segregation of traffic according to vehicle size can take several forms, including provision of lanes reserved exclusively for trucks, exclusive car lanes, or rules barring the largest trucks from all but a restricted network of the highest-quality roads.
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From page 168... ...
. The state studied construction of exclusive truck lanes as part of the project.
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From page 169... ...
The option of designating or constructing exclusive truck lanes was estimated to have no greater benefits and much higher costs (Trowbridge et al.
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From page 170... ...
ENFORCED EAT The federal government is not directly engaged in enforcing size and weight limits. Rather, federal truck size and weight laws include provisions imposing requirements on the states for enforcement of weight regulations.
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From page 171... ...
The following subsections summarize the available information on the extent of illegal overloads, the scope of permit operations, the cost of overweight/oversize operations, and the effectiveness of enforcement. Illegal Overloads A 1988 National Cooperative Highway Research Program study synthesized available truck weight data.
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From page 172... ...
devices in recent years has provided some new information about the frequency of overfoads, although uncertainties are introduced in converting the devices' readings to equivalent static load distributions, and data collection and analysis have not been designed for the purpose of assessing compliance with weight regulations. In WIM data from several hundred sites on all road systems in 18 states collected for the DOT Long-Term Pavement Performance program, roughly 12 percent of tandem axles exceeded 34,000 Ib (the federal maximum)
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From page 173... ...
Sixteen states have statutory gross vehicle weight limits greater than 80,000 Ib for highways other than the Interstates. Four additional 173
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From page 174... ...
. According to the TRB Truck Weight Limits study, if all illegally overweight axle loads were eliminated and the volume of truck freight carried remained unchanged, highway agency pavement costs would decrease by $160 million to $670 million annually (TRB 199Oa, 254-255~.
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From page 175... ...
At present, the effects of truck weight enforcement programs are generally not known in terms of (~) actual impact on weight-law compliance, (2)
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From page 176... ...
; targeting enforcement efforts (e.g., at repeat offenders and on roads with high violation rates) ; and developing information systems to monitor compliance, evaluate effectiveness, and direct resources.
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From page 177... ...
The Truck Weight Limits study committee recommended that Congress consider the following measures to strengthen enforcement: · Direct federal funding of state enforcement, possibly by amending the federal Motor Carrier Safety Assistance Program, which provides funding to states for enforcement of federal truck safety regulations; · Imposition of federal penalties for violations of federal weight limits on Interstate highways, or alternatively, mandating of minimum state penalties; · Federal provision for assessing penalties against the parties responsible for placing overweight shipments into commerce, that is, enforcement targeted at shippers as well as carriers and drivers; · Federal support for state measures to place overweight trucks out of service until they are offloaded; · Development of educational programs for judges and prosecutors regarding the overweight problem; and 177
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From page 178... ...
Although one member of the Truck Weight Limits study committee dissented from the report on matters concerning analysis of enforcement issues, that member endorsed this list of possible reform measures (p.
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From page 179... ...
Technology applications could greatly facilitate the administration of more complex size and weight regulatory approaches and enforcement schemes including the permit programs that exist today, as well as the federally supervised permitting proposed in Truck Weight Limits, self-enforcement such as the NRTC alternative compliance scheme, and performance standards. The purpose of the following discussion is not to suggest that technology is the solution to the enforcement problem.
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From page 180... ...
A dense network of sensors would be required for effective enforcement of route restrictions, while PrePass installations are located mainly along major Interstate corridors. · Repeat offenders Studies of weight enforcement have revealed the high proportion of violations accounted for by repeat offenders, but the states lack effective means of targeting enforcement at these 180
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From page 181... ...
would not be applicable. Databases and Information Systems Enforcement officials recognize that databases and information systems are the key to improving enforcement efficiency.
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From page 182... ...
Inclusion of weight violations in the determination of a carrier's safety rating has been proposed. The rationale is that a correlation is believed to exist between a carrier's size and weight violations and accident risk.
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From page 183... ...
The techniques now emerging include improved vehicle designs for better control and stability, information technology applications for control and stability and collision avoidance, streamlining the implementation of technology applications to improve enforcement, and changes in highway design. The benefits of most of these techniques in practice have not been measured, however.
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From page 184... ...
In summary, these evaluations include the following: · Measurement of the relationships between truck handling and stability properties (for example, rollover thresholds and accident risk; · Examination of whether essential trade-offs exist between safety costs and other truck operating costs per unit of freight services (for example, trade-offs between safety and cargo-carrying capacity) ; · Development of certification and monitoring procedures that would provide the opportunity for innovative vehicles to be demonstrated and evaluated; · Measurement of the relationship of vehicle characteristics other than static axle weights and spacing, in particular suspension and tire properties, to pavement and bridge costs; · Measurement of the relationship of size and weight law enforcement and size and weight violations to accident risk; · Monitoring of rates of violation of size and weight regulations by road class, type of trucking operation, and other characteristics that would allow enforcement to be effectively targeted; · Evaluation of alternative enforcement strategies, including applications of information technology for vehicle identification and automated enforcement, through planning studies and pilot .
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From page 185... ...
Department of Transportation FHWA Federal Highway Administration FMCSA Federal Motor Carrier Safety Administration LTSS North American Free Trade Agreement Land Transportation Standards Subcommittee NCHRP National Cooperative Highway Research Program NIDOT New Jersey Department of Transportation NRTC National Road Transport Commission OIG Office of the Inspector General, U.S. Department of Transportation RTAC Roads and Transportation Association of Canada SCAG Southern California Association of Governments TRB Transportation Research Board TXDOT Texas Department of Transportation VDOT Virginia Department of Transportation ARRB.
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From page 186... ...
NCHRP.1998. NCHRP Research Results Digest 229: Developing Measures of Effectiveness for Truck Weight Enforcement Activities.
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From page 187... ...
TRB.1990a. Special Report 225: Truck Weight Limits: Issues and Options.
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From page 188... ...
Truck Size and Weight Regulations. 1996 Semisesquicentennial Transportation Conference Proceedings, Center for Transportation Research and Education, Iowa State University.
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