March/April 1988
And you thought algebra was awful? Try figuring truck size and weight allowances to comply with your state highway regulations. Brace yourself for an unfigureoutable formula, a slew of mumbo jumbo, and more than a few no-sense rules. Or, better yet, read this article. It can help you understand existing laws … and may motivate you to seek change.
By Debra R. Levin
Debra R. Levin is director of environment, trade, and transportation and assistant counsel for the Institute of Scrap Recycling Industries, Washington, D.C.
Does the following 250-word sentence mean anything to you?
... [The maximum gross weight to be allowed by any state for vehicles using the National System of Interstate and Defense Highways shall be twenty thousand pounds carried on one axle, including enforcement tolerances, on a group of two or more consecutive axles produced by application of the following formula:
W= 500 ( [LN divided by N-1] + 12N + 36 )
where W equals overall gross weight on any group of two or more consecutive axles to the nearest five hundred pounds, L equals distance in feet between the extreme of any group of two or more consecutive axles, and N equals number of axles in group under consideration, except that two consecutive sets of tandem axles may carry a gross load of thirty-four thousand pounds each providing the overall distance between the first and last axles of such consecutive sets of tandem axles is thirty-six feet or more: Provided that such overall gross weight may not exceed eighty thousand pounds, including all enforcement tolerances, except for those vehicles and loads which cannot be easily dismantled or divided and which have been issued special permits in accordance with applicable state laws, or the corresponding maximum weights permitted for vehicles using the public highways of such state under laws or regulations established by appropriate State authority in effect on July 1, 1956, except in the case of the overall gross weight of any group of two or more consecutive axles, on the date of enactment of the Federal-Aid Highway Amendments of 19 74, whichever is the greater (Section 127 of Title 23, U.S. Code--"The Federal Weight Structure")
This remarkable slew of mumbo jumbo means a great deal to processors across the country who are handling scrap in lugger, roll-off, and dump trucks, trailers, or semitrailers--any type of specialized hauling vehicle. In plain language, here's what you need to know: Truck weights for vehicles using the federal Interstate Highway System and federal-aid highways generally are controlled by federal, not state, law. The single-axle limit is 20,000 pounds; the tandem-axle limit, 34,000 pounds; and the gross vehicle limit, 80,000 pounds.
These gross and axle weight limits are restricted further by the federal bridge formula, a standard that controls overall weight in relation to the spacing of axles. The formula was originally proposed in the 1950s but was not adopted as a federal requirement until 1975. One problem with the formula is that it's hard to figure. A Federal Highway Administration (FHWA) chart is easier to use in determining the more restrictive limitations imposed by the bridge formula. For a five-axle combination vehicle to carry 80,000 pounds and comply with the federal bridge formula, the distance between the two sets of tandem axles (axles two and five) must be at least 36 feet; the distance between the first and fifth axles must be 51 feet.
States may allow exceptions to the federal weight law, based on the so-called "grandfather clause." This authorizes states to allow vehicles to operate with weights and configurations that could have been allowed as of July 1, 1956, or January 4, 1975, notwithstanding the federal requirements. Such exceptions include:
single-axle limits greater than 20,000 pounds;
tandem-axle limits greater than 34,000 pounds;
gross vehicle weights in excess of 80,000 pounds;
a wheelbase in connection with total gross weight shorter than the federal bridge formula allows; and
special permit systems allowing greater axle weight, gross weight and/or axle spacing limits.
By having the power to withhold Interstate Highway funds if the state does not comply with the federal standards, federal law effectively prohibits any state from raising its limits on the Interstate Highway System if in 1956 or 1975 the state could not have allowed exceptions similar to those listed. The federal weight limits are enforced by the threat to cut off a state's Interstate Highway funding, unless, of course, the state can claim a grandfathered exception. While no officially recognized census has been taken of states with grandfather status, authorities estimate that as many as 40 percent may have made allowances for alternative limits. Thus, weight limits are governed by genealogy, rather than by any rational system that recognizes the capacity and design of today's highways, bridges, and vehicles.
Translated into plain language and measured by practical experience, Section 127, "The Federal Weight Structure," means trouble for recycling economics. The industry's problems with the federal weight structure are simple:
Compliance with the federal standards increases costs and decreases profitability.
Vehicles in scrap service today can safely carry heavier loads than allowed by federal law.
Exceptions to the federal law that allow heavier vehicles to operate in some states prove that higher limits are feasible.
The lack of a uniform national law with higher weights hampers economical interstate movements.
Any solution that involves state government will be only partially effective in relieving industry concerns. Unfortunately, to achieve a federal solution, scrap processors in combination with other affected industry groups must be prepared to engage highway engineers and legislators in a legal and technical discussion aimed at uprooting conventional wisdom.
State Government's Role
To their credit, state officials are being helpful when local constituencies persistently voice their needs. In more than one notorious struggle, federal dollars were the hostage and FHWA recognition of grandfather status, the ransom.
A case in point is Massachusetts. Year after year the commonwealth was in limbo because FHWA withheld certification that Massachusetts was complying with Section 127. Yet in 1979, at the request of the Commissioner of the Department of Public Works, the Attorney General documented in a legal memorandum the authority of the Department to issue reducible load permits on both July 1, 1956, and January 4, 1975.
Tough words between fleet owners and the Department and between the Department and FHWA, plus a $300,000 educational effort financed by the construction industry, yielded an agreement on a program. The agreed-on program lets vehicles obtain annual divisible load permits to gross 73,000 pounds (three-axle), 87,000 pounds (four-axle), or 99,000 pounds (five-axle combination). Other significant program features are a dramatic increase in overweight fines, a manufacturer certification of equipment for the permit weight, an owner certification that nothing has been done to downgrade the manufacturer's rating, and posting of those bridges unable to carry permit loads.
The Massachusetts experience illustrates what industry is likely to encounter elsewhere: initial reluctance by the state to defy FHWA, gradual conversion of highway department officials, political setbacks when an accident such as a bridge collapse prompts the reflex reaction of blaming "heavy" trucks, and official support for a workable program synthesized from the concerns of all involved.
A key ingredient in the success of the Massachusetts Construction Industry Council was the presentation of industry-funded consulting and engineering studies that demonstrated the engineering soundness and safety and environmental benefits of the permit program compared to the federal standards.
While the initial concern that led to the federal standards, and particularly the bridge formula, was the alleged punishment heavy vehicles cause to bridges and roads, reasons for preferring this weight structure over the permit program soon included references to traffic safety risks allegedly associated with heavy vehicles. Neither concern is valid, as demonstrated by the studies presented in Massachusetts. A Cambridge consulting firm contributed findings on the relative traffic safety of heavy-weight versus medium-weight trucks. Among those findings:
Trucks generally have accident rates that compare quite favorably with those of automobiles.
Trucks in the very heavy weight range have accident rates, based on mileage, that are similar or superior to those for medium-weight trucks.
Fewer larger, heavier trucks are needed to accomplish the same task as smaller, lighter trucks; so the number of accidents may be reduced.
Vehicle weight is but one factor influencing accident risk. To the extent that weight affects accident experience, it is itself greatly influenced by factors such as operator competence and vehicle condition.
FHWA’s response to the study is notable. While they agree that heavy trucks have lower accident rates based on mileage than medium trucks and that accident rates for cars and trucks are similar, they retort that the fatality rate in truck accidents is greater. But, even if this is true, the remark has no relevance to a comparison of safety records for medium-weight and heavy-weight trucks.
The engineering analyses developed for presentation in Massachusetts are now the basis for recommendations by the specialized hauling industry to replace the federal bridge formula--at least for vehicles carrying heavy bulk materials, such as those used in the scrap recycling industry.
The Massachusetts exercise influenced neighbor Connecticut. In Connecticut, the weight structure issue was presented differently. Again, the industry engaged consultants. A cost-benefit analysis compared several scenarios with the existing system--namely, 22,848-pound single-axle limits (with tolerance), 36,720-pound tandem-axle limits (with tolerance), and higher gross vehicle weights associated with particular wheelbases. The significant comparisons considered as alternatives were the federal weight structure in its entirety and "optimal" limits defined as existing Connecticut limits plus 20 percent. The comparisons examined transportation costs, pavement impacts, bridge impacts, energy conservation, safety impacts, and environmental impacts.
Figure 1 shows cost comparisons. The scenario that decreases limits (federal) shows an increase in total costs; the scenario that increases limits (optimal) shows a decrease in total costs. The result for nonmonetary impacts are similar: Relative to the current limits, the federal limits produce greater fatality and injury accidents, greater air emissions, and greater energy consumption. The optimal limits are associated with a reduction in fatal and injury accidents, air emissions, and energy consumption.
The New York saga, too, shows that persistence pays. Economic impact data, a vehicle census, analysis of overweight violations, legal research, and political visibility produced a special permit program for New York State specialized haulers. For more than seven years the various state associations representing segments of the construction industry pressed the case. Fortified with an attorney general's opinion backing New York's grandfather status, evidence that other states have divisible load permits (permits for loads that can be divided into separate shipments), and the backing of the Teamsters and other industries operating heavy vehicles, the coalition achieved many of its goals in the 1985 session of the legislature.
Through 1994, divisible load permits can be issued for vehicles registered in New York before January 1, 1986, provided the permit weight does not exceed the manufacturer's recommended axle and gross vehicle weights. Annual fees range between $300 and $750 per unit. For a five-axle tractor-trailer, for example, the statewide permit (other than New York City) allows a gross vehicle weight maximum of 88,750 pounds, and the downstate permit (other than New York City), 120,000 pounds, where formerly the limit was 71,000 pounds. Overweight fines that were $100 now range from $50 to $7,000. Permit-holders exceeding the permit weight by as little as one pound can be fined $2,700.
Activity in other states illustrates what is possible when an industry group throws open the door provided by local law as it existed on July 1, 1956, or January 4, 1975.
By regulation, New Jersey provides a temporary exemption from the federal bridge formula through October 1, 1988, for tandem-axle dump trucks, five-axle dump trailers, two-axle dump trucks, tri-axle dump trucks, four-axle dump trucks, three-axle and four-axle ready-mix transit trucks, five-axle bulk carriers, two-, three-, four- and five-axle liquid bulk carriers, and intermodal ocean containers.
The scrap processing industry successfully requested a modification to extend the exemption for New Jersey-based fleets to out-of-state registered vehicles. The request was made, too, by the New Jersey Truck Association (NJTA) and the association for the asphalt industry. (The original "New Jersey" exemption was obtained by fuel merchants and lumber dealers along with NJTA.)
Two other industry groups have exemptions: the construction industry, with "constructor" vehicles, and the solid waste industry, with refuse vehicles. The refuse exemption provides relief from axle-weight limits when operating on state roads within 20 miles of the terminal.
The Maryland legislature in 1983 extended until April 1, 1985, the deadline for claiming an exemption from the "inner bridge" requirements of the federal bridge formula. The term "inner bridge" is normally used to refer to the distance between axles two and five. According to the Maryland Motor Truck Association, vehicles eligible for the exemption are:
registered in Maryland prior to December 31, 1983;
a two-axled straight truck that pulls a trailer;
a three-axled straight truck that does not have a Dump Service Tag;
a tractor that in combination with a semitrailer does not meet the interior bridge requirement of 36 feet between the centers of axles two and five; and
a semitrailer that in combination with a tractor does not meet the 36-foot interior bridge requirement. The inner bridge exemption expires in April 1991.
Maryland also exempts containerized cargo hauled under a permit. Permitted maximum weights are 21,400 pounds for single axle, 39,000 pounds for tandem axle, and 89,000 pounds for gross vehicle. Haulers must use only designated routes.
The inner bridge exemption was possible because Maryland had grandfather rights with a similar exemption dating from 1951. However, in the early 80s, the state gave up a portion of its grandfathered axle limits, reducing from 40,000 pounds to 36,000 pounds the maximum for tandem axles and placing an expiration date on this variation from federal law.
The containerized cargo exemption was advocated by the Maryland ports concerned that because Virginia port traffic had such an exemption, Maryland was at a competitive disadvantage without it.
Other Maryland vehicles with special weight treatment include dump trucks (e.g., single-unit, three-axle vehicles have only a gross weight limit, 65,000 pounds). A similar grandfathered exemption for dump semitrailers expires April 30, 1991.
These instances of states asserting their grandfather rights, while encouraging examples that economic weights are politically and legally achievable, are still limited. First of all, not all states are able to assert grandfather rights to provide the necessary relief from federal weight and bridge formula requirements on the Interstate Highway System. Second, much of the relief has been temporary. FHWA has asserted that a state cannot issue special permits on a regular and continuous basis, permit vehicles must comply with the bridge formula, and only weights and configurations actually allowed on the grandfather dates are grandfathered today. In settlement of actual or threatened lawsuits over states' rights and access to highway funds, FHWA has allowed states to issue permits for only two or four years--to allow vehicle owners to phase out equipment that does not conform to the federal weight structure.
The relief is unsatisfactory for other reasons, too. The agency appears to be insistent on having the last word, without acknowledging the legally correct position, namely, that the state is to determine the scope of the grandfather clause and that the clause applies to what could be--not what was--operated. Last of all, for vehicles crossing state borders to serve scrap markets, loading is constrained by the more restrictive state's law.
This lack of uniformity is problematic in several regards. It means certain equipment is inappropriate for particular trips, restricting logistical flexibility. It means tension between the dissimilar, albeit often more realistic, limits in grandfather-status states and the potentially greater, but more restrictive, federal uniformity. It means a new form and more numerous examples of the "barrier" state phenomenon that the Surface Transportation Assistance Act of 1982 was supposed to eliminate.
Federal Action Essential
Traditionally the states, under their police powers, have regulated motor vehicle weights. They have done this with some combination of rules based on limits for single-axle weight, tandem-axle weight, gross vehicle weight, axle spacing, divisible versus indivisible loads, and special permits.
In 1956, Congress created the Interstate Highway System as a program to provide financial assistance to the states for construction of a new national highway system. It is clear beyond dispute that in 1956 many states allowed gross weights and axle weights greater than the new weights proposed for the Interstate System. The legislative history shows Congress respected these state programs by expressly authorizing their continuation without sacrificing federal highway funding.
Nineteen years later, Congress revised Section 127. The amendments lowered the speed limit to 55 mph as a fuel conservation measure and raised the maximum gross vehicle weight to 80,000 pounds to offset the productivity lost by reducing speeds. For the first time, the amended Section 127 imposed weight limitations based on axle groupings. Under the new "Bridge Formula" the number and spacing of axles governed allowable weight. Once again, though, lawmakers were aware that many states had programs permitting weights greater than would be allowed under the new proposal. To protect the states, the 1956 grandfather clause remained in Section 127, and language was added to it that would avoid negating state schemes that varied from the federal bridge formula.
Following enactment of the 1974 Act, FHWA adopted a regressive interpretation of Section 127 and used it to badger states into giving up legitimately protected state practices that diverged from the federal weight structure. Montana and South Dakota went to court to defend their authority; the states' interpretation, not FHWA’s, was upheld. (State ex. Rel. Dick Irwin, Inc. v. Anderson 525 P.2d 564 [Mont. 1974] and South Dakota Trucking Assn. v. South Dakota Department of Transportation 305 N.W. 2d 682 [S.D. 1981]) By contrast, South Carolina, Maryland, and Georgia, to name a few, gave in to FHWA’s demands.
The Surface Transportation Assistance Act of 1982 (STAA) again amended Section 127. Lawmakers made 80,000 pounds a mandatory federal gross weight limit for all states, intending to eliminate the last barriers to interstate commerce interposed by the lower gross vehicle weight (73,000 pounds) within Arkansas,
Illinois, and Missouri. Congress also increased truck capacity for certain types of hauling by authorizing tandem trailer operations and wider vehicles.
However, the 1982 law made a potentially more valuable contribution to the cause of specialized heavy hauling. In the STAA itself and in its legislative record are explicit Congressional instructions to FHWA on interpreting states' grandfather status. At issue was who determines what could have been lawfully operated on the grandfather dates and, thus, the scope of the state's exception to the federal weight standards. The agency was prohibited from denying monies to any state which determined for itself that vehicles or vehicle combinations could be lawfully operated on July 1, 1956, at higher single-axle, tandem-axle, or gross weights, or on January 4, 1975, with differing gross weights on axle groups.
In explaining the phrase "which the state determines," Senator Symms, the Senate floor manager, said, "The language added 'which the state determines' will resolve these outstanding conflicts. It is intended to apply to situations like Montana where a State court, or like Massachusetts where a State attorney general, or Oklahoma where a State agency, after having carefully considered the facts in that State, is on record as having made a final determination as to what is allowable under the grandfather clause." (128 CR S14997 Dec. 16, 1982)
STAA also resolved the issue of what could be grandfathered. In the words of the House floor manager and Surface Transportation Subcommittee Chairman Glenn Anderson, "the federal bridge formula and axle limits do not supercede or nullify the grandfather clause. A state may issue special permits for divisible loads that do not comply with the bridge formula or the axle limits, if authorized under those laws as provided in the grandfather clause." (128 CR H8917 Dec. 6, 1982)
In September 1983, FHWA issued proposed rules to implement Section 127 as amended by STAA. The proposal was adopted as final, virtually without change, in June 1984. Undaunted by its failure to prevail in the judicial and legislative forums, FHWA issued regulations superimposing the federal bridge formula over any differing state weights if the state did not cover vehicles under an axle spacing formula or "group of axles" table. FHWA arrogated final review of a state's grandfather claim, despite the "state determines" language. The agency also superimposed the bridge formula as a constraint on any state program of special permits for divisible loads. The rules effectively prohibited the states from modifying a grandfathered program after 1956 or 1975 (or reinstating one after relinquishing it in a dispute with FHWA) by denying grandfather protection to the modifications. The rules limited the special status to vehicles actually in operation in 1956 or 1975, despite statutory language protecting vehicles that could have been lawfully operated. Consequently, states with the authority to issue divisible load special permits which did not exercise that authority could not issue permits at any time in the future. The bottom line is that there are new restrictions on states (and trucks operating in such states) that previously were not subject to these limitations.
Based on his experience over the years with the agency, Larry Snowhite, attorney for the National Truck Weight Advisory Council (NTWAC), has opined that in FHWA’s view, apparently the only good truck is a garaged truck. The final June 1984 regulations led to a NTWAC court challenge. It was ultimately dismissed on procedural grounds, but stimulated FHWA to accelerate serious reevaluation of its treatment of the specialized hauling industry.
Members of the specialized heavy hauling industries, like scrap processors, are vexed not only by FHWA’s stubborn loyalty to a discredited legal interpretation and engineering practices that are outdated, but particularly by the inadequacy of the federal bridge formula to serve the economy.
It is easy to see how a legislator can conclude in 1988 that all is well with the feds, the states, and the heavy-truck operators. The perception is that the much-celebrated STAA demolished the truck weight barrier and, by allowing larger vehicles, improved trucking productivity. While that may be so for the long-haul 18-wheel tractor-trailer that most legislators think of when they think of "trucks," that is not the case for specialized hauling vehicles.
Take the case of a five-axle roll-off trailer combination that weighs 42,000 pounds empty. If registered in Pennsylvania for 73,280 pounds or less, it can carry 22,000 pounds on a single axle and 36,000 pounds on a tandem, and it is not subject to the bridge formula. The exact same vehicle, with a total wheelbase of 37 feet 5 inches and an inner bridge of 24 feet 2 inches, if registered for anything over 73,280 pounds--say, 80,000 pounds--is subject to the bridge formula. Therefore, it will be unable to maximize at the full 80,000 pounds and is limited to only 7 1,000 pounds. If the vehicle travels to Ohio another set of rules applies, while a trip to New Jersey subjects the operator to totally different regulations.
The truth is, STAA as interpreted by FHWA affords no productivity gain whatsoever to specialized heavy hauling equipment. The difference in the example between the maximum gross and tare weights is a cargo of 38,000 pounds; the difference between the allowed bridge formula gross of 71,000 pounds and the tare weight is a cargo of 29,000 pounds. Net the first cargo against the second and you have a productivity sacrifice directly attributable to the bridge formula: a cargo loss of almost 25 percent per trip. There is a financial penalty as well if, as is frequently the case, due to the nature of scrap, the load shifts when pulling a rolloff container onto the chassis, overloading the rear axles. But processors, nevertheless, are paying the sharply higher "heavy vehicle use tax" required as the trade-off for the alleged productivity boost--a boost they can never realize under the federal weight law.
It is logical to ask why the industry is not replacing its vehicles with new, larger equipment. Scrap processors are not running the double trailers and the 6-inch wider cargo boxes allowed by STAA because weight, not cubic capacity, is the problem. That is, the weight law precludes loading to the full existing cubic capacity, so expanding the allowable cubic volume is not addressing the problem at all. Scrap processors are not generally running roll-off trailers in tandem because the short distances and double handling that would be involved threaten recycling economics. And processors are limited in their equipment choices by the layout of scrap-generating and scrap-purchasing manufacturing plants they service but cannot redesign.
Heavy hauling industry criticism is leveled at FHWA because its grandfather clause interpretations balkanize weight regulation within a given state and between states. Yet the agency's overbearing effort to introduce uniformity via the bridge formula is repugnant, too, because the bridge formula itself is ineffective in dealing with the engineering issues in bridge and pavement design. It is also insensitive to the special needs of particular specialized hauling vehicles. The ultimate problem is that the federal law requires the bridge formula to regulate all kinds of vehicles. The consulting work presented in the Massachusetts debate documents many of the shortcomings of the bridge formula and other aspects of "conventional wisdom."
Bridge Formula Background
The purpose of the bridge formula is to protect roads and bridges from the damaging effects that can result if too much weight is concentrated at one point on the surface; protecting bridges, however, has been the dominant concern. Consider the problem of crossing thin ice: to walk upright could break the ice; distributing your weight more evenly across the surface by lying down and sliding might prevent the break.
Bridges are designed so that the stress produced by bridge loads will not produce permanent deformation in the structural elements. Key factors in bridge design include:
the ability of structural members to support the various loads, including live load (the weight of vehicles using the bridge), dead load (the weight of the bridge itself, and loads associated with other forces (wind, earthquake, thermal);
construction materials;
weather and environmental effects; and
anticipated traffic.
For the development of bridge design, several standardized design loads have been specified, notably the HS 20 truck and the H15 vehicle. The HS 20 has 72,000 pounds on three axles with 14 feet between axles one and two and from 14 to 30 feet between axles two and three. The H15 consists of two axles spaced 14 feet apart carrying a combined weight of 30,000 pounds. Bridges are identified by their corresponding design load. The bridge formula was developed as a means to limit gross and axle group weights to those that could be carried on existing H15 bridges. But there are about 800 H15 bridges on the Interstate System out of over 52,000. While no one would endorse risking the potentially catastrophic consequences of overloading H15 bridges, it is clear that the formula denies the use of the full load-bearing capacity of superior HS 20 bridges that comprise the majority on the lnterstates. That is, rather than realize the full benefit of the existing inventory of bridges while protecting the limited number of H15 design bridges, our public policy honors the weakest link.
To appreciate the margin of safety incorporated in bridge design and to understand a proposed uniform national alternative to the federal bridge formula, some terms must be understood.
Stress is a function of the "load on," "length of," "shape of," and "area of" a beam, expressed in pounds per square inch.
Strain is the amount of stretch in the steel, expressed in inches per inch.
Yield stress is the point to which the strain is proportional to stress and the steel is elastic. After strain, steel returns to its original shape.
Ultimate stress is the maximum stress the steel can take before failure, meaning the beam continues to yield without additional loading until it reaches complete rupture.
Design stress is designated by the American Association of State Highway and Transportation Officials (AASHTO) as 55 percent of yield stress.
Permit stress is designated by AASHTO as 75 percent of yield stress. It is the stress generally allowed for issuing permits.
In the study conducted by C.E. Maguire, the consultant examined the effect of heavy trucks on bridges and roads. A stress/strain curve was plotted for a test bridge, and curves for different vehicle configurations were superimposed. For vehicles common to the construction industry, weights from 46 to 150 percent greater than allowed under the bridge formula did not even reach permit stress. Maguire concluded that trucks with Massachusetts permits did not result in stress on the main beams that exceed the design stress; decks are more than safe and fatigue is not a problem.
H.W. Lochner confirmed the Maguire results and strengthened the case for allowing greater weights by accounting for the "Tennessee effect." Tennessee Department of Public Works engineers found the deck and diaphragm of the bridge distribute loads to beams far more effectively than originally believed. Though AASHTO specs direct engineers to account for more than one vehicle being on the bridge at a time by assigning loads to each beam at 63.8 to 68.2 percent of a truck, beams in a bridge designed for 3.3 trucks bore only 58.7 percent of the calculated stress. So, notwithstanding the restrictiveness of the bridge formula, heavier trucks can safely use existing bridges.
Lochner also looked at the relationship between higher payloads and construction costs. Like the findings in the Connecticut study, Lochner's findings demonstrate the very positive benefit/cost effect of increased weights. A 50 percent increase in design live load is associated with a 100 percent increase in payload. The added cost is a four percent increase in the cost of new construction and a 12 percent increase in the cost of rehabilitation.
Long after creation of the bridge formula, it came to be used as an argument for protecting pavement. So, the construction industry asked consultants to determine whether there was sufficient data available to pinpoint the contribution of truck weight to pavement damage. In the 1940s AASHTO's predecessor organization studied pavement performance to aid in improving pavement design. The study warned: "Generalizations and extrapolations of these findings to conditions other than at the road tests should be based upon experimental or other evidence of the effects on pavement performance of differences in climate, soil type, materials, construction, and maintenance practices." Despite this warning, the AASHTO road test results became engineering doctrine for a myriad of uses.
Maguire reviewed the study and drew these conclusions: The AASHTO road test, due to the manner in which it was conducted, dictated the conclusion that heavy trucks cause deterioration of pavements: the test was designed for the roads to fail. There is evidence that roads not allowing trucks must be repaved at about the same frequency as those with truck traffic. Pavement failure is due to a combination of factors.
Lochner's reaction was similar: If pumping is eliminated and rigid pavements are properly designed and maintained throughout their design life with a properly compacted three- to nine-inch gravel base course, they will not fail due to loading during their design life. The same is true for a flexible pavement. Overlays to flexible pavement are so effective that they not only add thickness to the roadway surface, they increase the bearing capacity of the roadway to values exceeding the originally constructed roadway.
A third study also criticized the misuse of the road test results. Carmichael et al. noted, "One of the basic concepts of the [AASHTO] experiment was to study and evaluate the performance of pavements and bridges through failure. Since failure was thus essential to the success of the research, all bridges and a substantial portion of the test pavements were designed to fail or otherwise show severe distress under test traffic. The direct comparison of types of pavements or bridges was not the intent of the experiment."
In the case of pavement, FHWA and others have used the AASHTO road test results to misallocate the cost of maintenance to weight. The bridge formula also is based on studies begun in the 1940s, when construction technology was primitive compared to today's standards. The bridges that the formula was calculated to protect do not meet present design and construction standards and have not been built for years. Older bridges remain, but they are few and not widely dispersed across the country. FHWA has acknowledged that the bridges prevalent on the Interstate System today are capable of withstanding significantly more stress than would be allowed by the bridge formula. It is sheer delusion to pretend that ultraconservative truck weight limits are an effective substitute for proper bridge design, proper construction standards, and adequate maintenance. A safe and economical alternative to the federal weight structure is long overdue.
Efforts to Promote Change
Efforts to promote change are under way.
The National Truck Weight Advisory Council, of which the Institute of Scrap Recycling Industries is a member, is a broad-based organization of individual companies and state and national associations representing the specialized hauling industries. Its goals have been to educate government officials, the public, and the press about the unique needs of the specialized hauling industries; to develop an alternative regulatory system to the federal bridge formula and weight limits; and to protect state grandfather rights and extend authority to adopt optimal weights to all states. These efforts are beginning to bear positive results. First, FHWA is recognizing specialized hauling vehicles as a separate class that merits separate treatment. Second, alternatives to application of the federal bridge formula and weight limits to specialized hauling vehicles are being explored on several fronts.
In the last highway funding law, Congress directed the Transportation Research Board to report on the effects of limitations imposed by the bridge formula, including an assessment of the potential costs and benefits of the formula, an examination of alternative means of regulating truck weights on bridges, and particularly, alternatives for specialized hauling vehicles. The Board is also to look at the repeal of the grandfather clause. The report must identify optimal axle loading and spacing requirements that take into account all costs and benefits to business, government, and the general public.
The completed study is due by March 1990. The committee that will conduct the study has just been named; Louis Nappi, chairman of NTWAC, is a member, and NTWAC will have formal observer status.
A related study, due in 1989, has been contracted for by FHWA. It, too, examines repeal of the grandfather clause and the practical impossibility of specialized hauling vehicles to comply with federal requirements. The handwriting is on the wall: FHWA will at some point seek legislation to repeal the grandfather clause. NTWAC is working with FHWA on that study to assure that specialized hauling vehicles will not be forced to comply with the bridge formula and may, instead, be subject to an alternative regulatory system.
NTWAC has developed an alternative regulatory system that would assure adequate protection of bridges and roads, while optimizing transportation efficiency by allowing the operation of vehicles that maximize productivity, safety, and environmental protection. The program calls for states to establish maximum gross and axle weight limits based on live load moment criteria that could not exceed 55 percent of yield stress on an HS 20 bridge, provided the vehicle does not exceed the manufacturer's gross vehicle weight rating. The state would also be authorized to adopt a program of issuing special permits to allow vehicles to operate with configurations and maximum gross weights that would not exceed the permit stress, which is 75 percent of yield stress on the HS 20 bridge, or the point at which permanent deflection occurs. Specialized hauling vehicles would not have to comply with the bridge formula. A vehicle operating with a valid permit in one state would be given reciprocity by other participating states. The state's permit program would have to assure that the permit vehicle can safely carry the permit load and the state would have to post and replace, on a priority basis, H15 bridges on the Interstate System.
This program would replace the existing regime of Section 127 as it applies to specialized hauling vehicles. It would eliminate the legal controversy over which states have grandfather protection: Each state would have the authority to establish prospective optimal limits within the bounds set by current, sound engineering practice. But no state would have to roll back any weight now allowed for such vehicles.
The NTWAC proposal would be of particular benefit to the specialized hauling segments of the trucking industry. Specialized hauling vehicles have three key features:
When loaded to the manufacturer's rated capacity, the vehicle is not capable of meeting the federal bridge formula limits.
The structural design or specialized equipment on the vehicle for handling the load results in a heavy tare (empty) weight.
Maneuverability and stability needs on and off the highway eliminate configurations that add length and, in turn, add axles. Specialized hauling vehicles constitute only 1.6 percent of all vehicles registered as heavy hauling trucks (over 50,000 pounds loaded), according to the 1982 Census of Transportation. Generally, they are empty for one direction on a round trip.
The increase in weights would be tied to posting and upgrading, where necessary, of substandard bridges on the Interstate System; upgraded weight enforcement; and increased penalties for noncompliance.
The first opportunity to implement this alternative may come as a result of NTWAC's lawsuit against FHWA’s June 1984 regulations. A result of the negotiation process arising from the suit was that, concurrent with the District Court's dismissal of the suit, FHWA offered to conduct a demonstration project, at a minimum, in New York, New Jersey, and the New England states that comprise FHWA’s Region I to show its feasibility. NTWAC, FHWA, and the states are discussing ways to implement the program. States such as New York and
Massachusetts, which have
programs already based on the proposal, would no longer be under the threat of withheld monies; FHWA would shift its attention to enforcement. FHWA would cease to challenge those states that issue permits under grandfather rights. In exchange, NTWAC and FHWA would work together to implement the alternative regulatory system. The objective is for FHWA to support state officials to extend or adopt permit programs for interstate travel, notwithstanding the permit vehicles not meeting the bridge formula or federal weight limits.
Heavy haulers may have one more card to play. FHWA has announced it intends to issue new regulations that will allow the states to decide the scope of their grandfather status. States will be asked, prior to a specific deadline, to document their grandfather rights, specifically including specialized hauling vehicles, which would be recognized by FHWA. Though FHWA has not yet published this notice in the Federal Register, members of the heavy hauling industries in the mean time can develop at the state level the kind of coalition that NTWAC has achieved in Washington. The ready-mix concrete, asphalt, solid waste, and scrap processing industries can pool legal and political resources to make a case for states' rights (and safe, economical trucking).
States will, thus, be presented with an opportunity in the short term to defend current permit programs and to justify new ones, provided they can find legal authority under the grandfather clause. (States without grandfather status would remain subject to federal requirements.)
However, just having grandfather authority does not assure acceptance by a state of any permit program. But, the NTWAC/FHWA framework provides states with a sound, defensible basis for allowing specialized hauling vehicles to operate at realistic weights. The states should be far more willing to adopt a permit program if endorsed by FHWA--or, at least, that is NTWAC's belief.
For the long term, the NTWAC/FHWA framework can be the basis for a federal statutory exception to the bridge formula and weight limits, an outcome essential if, as FHWA actions suggest, the grandfather clause soon is repealed.
Certainly, those in the heavy hauling industries have an interest in reviewing state statutes, regulations, and administrative practices to determine if there is a basis for grandfather status. In conjunction with that interest, heavy-hauling industry members should continue to educate government officials about the special needs of specialized hauling vehicles.
[SIDEBAR]
Live Load Moment
The NTWAC/FHWA alternative regulatory framework is based on the live load moment curve. That curve is as individualized as a thumb print. Two five-axle combinations with the same gross weight but differing wheelbases would generate two unique curves.
An engineer uses data on the bridge type and the vehicle configuration being analyzed. The NTWAC/FHWA program is based on the H20 bridge type.
The engineer's objective is to find the maximum loading of a vehicle so that the corresponding live load moment curve lies below either the line representing design stress for the H20 bridge or the permit stress of the same design bridge. First, the diagram plots the live load moment stresses for H20 bridges of spans 40 to 160 feet long. The design stress curve is labeled Fb = .55Fy (inventory rating). The diagram also plots the permit stress labeled Fb .75Fy (operating rating).
Truck A dimensions are 11 feet 5 inches between axles one and two and 5 feet between axles two and three. The vehicle gross weight is 80,000 pounds. If the Truck A curve is below the design stress curve, the vehicle can operate without a permit. As it happens, for all bridge spans analyzed, the engineer's plot of the Truck A curve lies between the design and permit stress curves for all H20 bridge spans analyzed. Under the NTWAC proposal, this particular three-axle vehicle can operate at 80,000 pounds, provided the manufacturer's gross vehicle weight rating is not exceeded.
Truck D dimensions are 16 feet 5 inches between axles one and three; 25 feet between axles two and five; and 36 feet 5 inches between axles one and five. The vehicle gross weight is 110,000 pounds. The Truck D curve also lies between the design and permit stress curves so a permit is necessary.
A truck would be registered at the maximum gross vehicle weight that generates a curve below design stress or, if the operator obtains a special permit, at a maximum weight that generates a curve between design and permit stress. In no instance is a truck allowed to carry more than the manufacturer's certified gross vehicle weight rating. For specialized hauling vehicles, the live load moment curve replaces the federal bridge formula and the federal gross and axle weight limits as the standard for determining the allowable loading configuration.
And you thought algebra was awful? Try figuring truck size and weight allowances to comply with your state highway regulations. Brace yourself for an unfigureoutable formula, a slew of mumbo jumbo, and more than a few no-sense rules. Or, better yet, read this article. It can help you understand existing laws
and may motivate you to seek change.