ferred trailer lengths. His analysis shows, for example, that at least 14 people were
killed in triple-trailer crashes alone from 1980 through 1988. These findings directly
confound the claims made by the American Trucking Association that only nine (9)
people died in all LCV crashes throughout the 1980s.^
These findings by Mingo show that LCV fatal crashes are approximately ten times
or more the levels claimed by the trucking industry. Nevertheless, the GAO's basic
claims on the inadequacies of LCV crash reporting and data collection/analysis are
generally accurate. In fact, prominent safety researchers such as Roger Mingo are
the first to admit that,
the current system of ad hoc state monitoring with no consistent quality control
results in the opportunity for much misinformation regarding LCV accidents.
Since the current haphazard system of LCV accident monitoring is totally inad-
equate, it is unlikely that it could be relied upon adequately to monitor the
much higher volume of LCV traffic that the ATA proposal for expanded LCV
operations would produce.''
Even the TIFA data base from the University of Michigan is acknowledged by
Mingo to be incomplete. His estimates of LCV crashes are highly conservative be-
"^ Roger Mingo, et al., "Safety of Multi-Unit Combination Vehicles," R.D. Mingo and Associates,
and the Scientex Corporation, Washington, D.C., September 1990. Also see Roger Mingo, et al.,
"Accident Rates of Multi-Unit Combination Vehicles Derived from Large-Scale Databases," 70th
Annual Meeting, Transportation Research Board, Session 163, Washington, D.C., January 16,
1991. Attachment A, Table 1 and 2.
^ Roger Mingo, et al., "Safety of Multi-Unit Combination Vehicles," op. cit., p. 1.
3 Id.
•*Roger D. Mingo, "Longer Combination Vehicle Fatalities from Special Trucks Involved in
Fatal Accidents' (TIUS) Tabulations," R.D. Mingo and Associates, May 17, 1991. Attachment A,
Table 2 and 3.
^ Roger D. Mingo, "Longer Combination Vehicle Fatalities from Special Trucks Involved in
Fatal Accidents' (TIFA) Tabulations," op. cit., p. 1.
*Id., p. 2. For trucking industry claims on LCV fatal crash involvements, see, e.g., Transport
Topics, April 8, 1991, p. 4.
â– 'Mingo, "Longer Combination Vehicle Fatalities * * *," op. cit., p. 1.
89
cause TIFA records "accidents with unknown configurations, known combination ve-
hicles with unknown numbers of trailers, and known doubles with unknown trailer
lengths and overall vehicle lengths." Furthermore, an additional danger in data ac-
curacy is the self-reported vehicle and trailer lengths without independent verifica-
tion. Lastly, the TIFA accidents Mingo analyzed for LCV crashes do not include any
adjustment for missing information; it is probable that his final conservative esti-
mates are even more oi an underestimation of total LCV accidents. ^
With these caveats in hand, I would like to supply for your review the two tabula-
tions of LCV fatal crash involvements provided by Mingo in his May 17, 1991 study,
supplemented with two bar-graph visualizations of his findings (provided as Attach-
ment A). In addition, I think I would be very valuable to the Committee to provide
a serial recitation of the major defects in crash data collection with regard to the
accurate discrimination of LCV accident involvement:
• Total LCV vehicle-miles-travelled is a tiny proportion of annual combination
truck vehicle-miles-travelled. Consequently, no specific LCV configuration is used
enough to allow accurate estimates of the fatal involvement rates or injury crashes
for each of the three main types (i.e., turnpike doubles. Rocky Mountain doubles,
and triples).
• On a nationwide level, we have no reliable travel data for LCVs and no reliable
configuration reporting.
• Wide variations exist among states on truck and, in particular, LCV accident
reporting. Some states collect configuration data, others do not.
• States collecting configuration data use different definitions, making it difiicult
to aggregate crash data by each LCV type on a national or even multi-state level.
• Some states provide relatively accurate information about certain aspects of
truck crashes, many cannot.
• As of 1991, vehicle classification is included in the accident reports of 22 states,
but not in the remaining states.
• General trailer type is reported in only 20 states.
• Number, size, and character (e.g., kinds of axles) of trailing units are reported
in only 14 states.
• Due to these data shortcomings, we cannot judge the safety records of each
type of LCV in comparison with single-trailer combinations. For example, Mingo,
supra, found a way to discriminate conservative estimates of triples involvements,
but could not use the available data bases to distinguish short doubles crashes from
Rocky Mountain or turnpike doubles crashes.
• All LCV studies have severe limits in sample size and data accuracy.
Although some of these data shortcomings circa 1991 should be corrected by the
national use of the National Governors Association recommended truck crash re-
porting format, it is unknown to what extent the states have implemented these im-
provements by late 1994, or to what extent all of the data deficiencies itemized
above will be rectified by the NGA's data collection system even if arguable full com-
pliance with the form was achieved.
I'd like now to turn to the issue of pavement damage and bridge deterioration due
to heavy trucks, especially LCVs. At the threshold, it should be emphasized that,
although the GAO in both its 1994 LCV report and in Mr. Kenneth Mead's oral tes-
timony before Senators Exon and Hutchison claimed that LCVs would damage roads
and bridges no more than "ordinary" trucks, the GAO itself points out, as I indicate
in my own written testimony submitted for the hearing record, that the
"[njationwide use of LCVs could generate additional costs to reconstruct bridges be-
cause the gross weights of LCVs may exceed levels considered safe on some
bridges."^
The reasons for this are very well-known: first, no combination vehicles operate
more oflen under overweight permits than LCVs. The whole point of an LCV is to
carry much larger amounts of cargo. Except for very light cargo, "cubing out" a tri-
ple or turnpike double will almost always exceed both federal and states gross
weight limits and oflen axle limits as well. Therefore, LCVs routinely seek over-
weight permits to operate these configurations far above nominal weight ceilings.
*Id., p. 3. Mingo goes on to point out that the TIFA data show cargo-carrying trucks with
two full trailers sometimes called triples, sometimes not. Certain hybrid rigs with medium-
length trailers are sometimes coded as LCVs, sometimes not. Moreover, there are other vehicles
with incomplete or inconsistent information which disallow accurate identification. "Together,
definitional vagaries and incomplete vehicle information create a potentially significant
underestimation problem." Id.
^Longer Combination Trucks: Potential Infrastructure Impacts, FVoductivity Benefits, and
Safety Concerns, GAO/RCED-94-106, August 1994 ("1994 LCV Report"), p. 22.
90
including the 80,000 pound federal limit as well as above even more generous gross
limits exercised by several states pursuant to their grandfather rights.
To oversimplify somewhat, bridges suffer deleterious stress in response to the
total weight of a rig as concentrated in the given area of the span.^° This deflection
or "bending moment" causes both compression of certain structural members and
the stress of other members (that is, stretching forces). Shear forces are also impor-
tant indicators of bridge strength and excessive shear forces can lead to rapid dete-
rioration and failure of certain structural features. It is important to mitigate the
effects of total gross weight by controlling the transmission of weight to the bridge
by, in part, requiring certain minimum spacing requirements of axle groups on a
combination truck. Tnis is the purpose of the Bridge Formula B of 23 U.S.C. § 127.
It means that certain combinations cannot even achieve the legal Interstate system
maximum of 80,000 pounds due to improper axle spacings. All other things being
equal, however, the better the distribution of total gross weight over a longer section
of the bridge deck, the better the mitigation of damaging bridge forces from heavy
loads. 11
On this basis, some LCVs at 80,000 pounds would arguably create less bridge
damage than an "eighteen-wheeler" at the same gross weight (given the additional
assumption of proper distribution of cargo to ensure axle weight limitations, such
as those of 23 U.S.C. § 127 are not exceeded for any axle(s) on the rig).i2 However,
as the GAO quotation indicates, there are very few economies of scale available to
the trucking industry by assuming the additional capital and maintenance expense
of operating a multi-trailer LCV governed only by the 80,000 pound gross weight
limit of current federal law. Except for very light cargo, LCVs can only achieve
economies of scale by operating considerably above current gross weight ceilings. In
those states where they are allowed, this is achieved by routine overweight permits,
many of which are clearly issued on an illegitimate basis (e.g., for "nondivisible"
loads, although the cargo is, in fact, easily divisible). Generally, speaking, a Rocky
Mountain double really only achieves its value of operating with its hybrid combina-
tion of a semi-trailer of 48 feet in length pulling a short full trailer ("pup") of 28
feet long when gross weights average close to the 100,000 pound range. Similarly,
triples when initiating a less-than-truckload trip are only economically efficient
when they exceed 100,000 pounds; and turnpike doubles, dedicated to long-haul
movements across several states to move freight similar to the same function of
long-haul rail transport, are really only efficient when weights range up to and be-
yond 130,000 pounds.i3
With regard to pavement damage, although the GAO in both its 1994 LCV report
and its testimony before your (Jommittee claimed that LCVs may even damage
pavement less than standard semi-trailer combinations, this claim is belied by the
GAO's accurate statement in its 1994 LCV report that LCVs not only average high-
er axle loads than conventional tractor trailers— thereby causing more damage than
"eigh teen-wheelers" — but that LCVs composed of short trailing units with single
axles, particularly triples, are prone to be a serious offender in axle-related damage
because all three "pups" ride on single axles. i"*
10 See the example supplied of accelerated bridge distress caused by large trucks in Attach-
ment B.
11 One of a myriad of short treatments of bridge stress from heavy vehicles is the very read-
able report authored by David R. Schelling of the University of Maryland, The Influence of
Heavy Trucks on the Overload and Allocation of User Costs on Bridge Structures, American
Automobile Association Foundation for Traffic Safety, Falls Church, VA, March 1985.
12 For example, if a turnpike double (tractor + 45- or 48-foot long semitrailer + 45- or 48-foot
long full trailer) were to gross at 80,000 pounds, its load, if properly allocated between the two
trailers, would be distributed over one single axle and four (4) Lanaem axles. The gross weight
would therefore be spread over a longer distance than the same maximum load in an "eighteen-
wheeler." In addition, this loadings would also be very favorable for mitigating pavement dam-
age because, with proper load distribution, each tandem axle would fall significantly short of
the maximum weignt of 34,000 pwunds allowed under federal law. Lastly, this condition addi-
tionally favors lower (lavement damage because tandem axles whose damage quotient is theo-
retically equivalent to single axles in fact damage piavement at much higher rate. But this hy-
pothesis, as I indicate in the text, is a contrary-to-fact conditional analysis because virtually no
turnpike double can gain any economic efTiciencies over a standard semi-trailer rig if it operates
at or below 80,000 pounds.
13 A good, short explanation of bridge damage from truck live loads is contained in the report
from the Transportation Research Board, "Twin Trailer Trucks," op. cit.. Appendix J.
1* 1994 LCV report, pp. 31, 5. It is important to appreciate the considerable increase in pave-
ment damage, ceteris paribus, by moving the same gross weight from a rig consisting predomi-
nantly of tandem axles into a rig in which the trailers ride on single axles. For example, the
Transportation Research Board of the National Academy of Sciences found in 1986 that, even
with an adjustment for fewer trips due to increased cargo capacity, short trailer doubles (west-
em doubles), which ride on single axles, will nearly double the net effect on flexible pavement
91
The point to be grasped here is that all pavement damage is measured by a con-
cept that is more than 30 years old: Equivalent Single Axle Loads (ESALs). The rate
of pavement damage by any axle or group of axles is measured on the basis of what
they create as pavement destruction in their equivalence to so many single axle
loads. This is the reason that, although federal law allows a maximum 20,000 pound
single axle limit on the Interstate system, it allows only a 34,000 pound limit for
a tandem or dual axle composed of two single axles with no more than five (5) feet
separating them. Why not a 40,000 pound limit? Because the engineering calcula-
tion of ESALs for a tandem axle shows that a 34,000 tandem axle generates ap-
proximately the same amount of pavement damage as a 20,000 pound single axle.
In fact, however, single axles on certain kinds of pavements substantially exceed the
damage potential of the weight of a supposedly equivalent tandem axle.
This should help to illuminate how pavement damage is aggravated by only slight
increases in any axle's weight: the increase in damage is exponenltial and rapid
with each small increment over a baseline. ^^ In fact, pavement damage rises as the
fourth power of axle weight. For example, let's assume that axle weights are prop-
erly distributed over the five axles (tractor steering single axle (=one axle); tractor
tandem drive axle (=two axles); semi-trailer rear tandem axle (=two axles)) of an
80,000 pound "eighteen-wheeler." On the basis of ESAL calculations, an increase of
only 5,000 pounds in the overall weight of the rig, that is, from 80,000 to 85,000
pounds, would result in only slight increases in each axle's weight over the federal
limits of 20,000 pounds single-axle, 34,000 pounds tandem-axle. i" Nevertheless,
pavement damage has now been increased by 130 percent. Moving axle weights up-
ward in concert with an increase from 80,000 pounds to 100,000 pounds — a common
overweight permitted condition in many states — increases pavement damage by
more than 260 percent. i''
References to these well-known pavement damage quotients calculated on the
basis of the ESAL concept probably number in the thousands. However, it is in-
structive here to note, in summary, some of the findings on pavement damage made
by the Federal Highway Administration in what are often internal studies which
we have secured through Freedom of Information Act requests. If the Committee
would like copies of any of these truck pavement damage materials, I would be
pleased to supply them for your staffs review and evaluation.
• Heavy trucks comprise 92 percent of total axle loads on the rural Interstate
system alone. ESALs by heavy trucks on the rural Interstate system have increased
by a rate of over nine (9) percent a year since 1970.^^
• In addition to excessive axle and gross weight limits in some states, the federal
government estimates that, overall, more than one-third of all heavy trucks on the
road at any time are illegally above federal and state weight limits. ^^
• Transport cost savings from improved truck productivity overwhelm associated
costs of increased highway and bridge destruction and of truck accident costs. Many
bridges and highway pavements would have to be considerably strengthened or re-
built to accommodate heavier and larger trucks.^o
• Current nonuniformity among the states with regard to truck weights, espe-
cially on non-Interstate highways, increases the economic advantage to motor car-
wear compared with tractor semitrailers on the basis of accepted pavement design/wear rela-
tionships. Twin Trailer Trucks, Transportation Research Board Special Report 211, Washington,
D.C., 1986, p. 166. Also see, Id., Appendix I which does an excellent job of explaining and com-
paring {lavement destruction among different types of trucks.
i^The original baseline calculation of heavy truck pavement damage was performed by the
American Association of State Highway Officials (AASHO — now the American Association of
State Highway and Transportation OfTicials (AASHTO)) by using a 18,000 pound single axle.
In a single traversal of a given stretch of pavement, AASHO found that a single axle weighing
18,000 pounds produces the same pavement damage as traversal of the same pavement by 9,600
automobiles. The AASHO Road Test, Report 5, Highway Research Board, Special Report 61E,
1962.
18 In reality, the distribution of weight of an 80,000 pound semi-trailer rig can often be about
12,000 pounds on the steering axle with 34,000 pounds on each of the two tandem axles=80,000
pounds.
^''B. Frank McCullogh and Eric D. Moody, "Analysis of Relative Pavement Damage for Se-
lected Truck Axle Weight Proposals in the State of West Virginia," 1994, p. 2.
18 Actual Truck Loadings on Highways in the United States and Their Effect on Pavement
Design, Federal Highway Administration, 1988.
19 Overweight Trucks — The Violation Adjudication Process, Federal Highway Administration,
July 1985.
20 An Investigation of Truck Size and Weight Limits: Final Report, U.S. Department of Trans-
portation, August 1981.
92
riers in several states while causing disproportionate costs in their highway pro-
grams and to competing modes of transportation.^^
• Pavement damage caused by trucks above 80,000 pounds — the preferred gross
weight of LCVs — is captured inadequately by current heavy truck user fees. In fact,
as gross weights move upward, increasingly heavy trucks, especially LCVs, pay a
smaller and smaller share of their proportional user fee responsibilities. As a class,
combination trucks registered above 75,000 pounds gross weight pay only two-thirds
of their cost responsibility.22
• However, cost allocation studies typically obscure individual vehicle user fee
deficits by embedding them within very broad user classes. It is likely that high-
annual-mileage, very heavy axle-load vehicles pay less than a third of their individ-
ual cost responsibilities. Unfortunately, both the Federal government and a number
of states have encouraged an excessive shift to heavy-axle weight commercial vehi-
cles.23
• Similarly, according to various studies conducted by the Federal Highway Ad-
ministration and university consultants, the heaviest overweight combinations, es-
pecially multi-trailer rigs with single axles such as triples, can be calculated to pay
only about one-fifth of their actual cost responsibility.^^
• The number of divisible load multi-trip permits for overweight trucks has in-
creased by more than 300 percent since the Symms amendment to 23 U.S.C. § 127
in 1982.25
• Domestic Freight tonnage, now at 2.9 billion tons of annual goods movements,
will increase 30 percent by the year 2000, vehicle-miles-travelled will increase 31
percent, and the number of freight-carrying trucks will increase by over eight (8)
percent to three million commercial vehicles.^^
This last projection of truck traffic by a major trucking ofiicial ought to provide
appropriate emphasis of the potential for further increases in pavement and bridge
damage by heavy trucks. If the LCV freeze were lifted and/or if NAFTA negotiations
were to result in higher axle or gross weight limits for U.S., Mexican, and Canadian
trucks travelling our federally assisted highways, these projections of trucks, truck
tonnage, and truck mileage will not only be revised upward, but will be accom-
panied by increases in infrastructure damage because trucks will be heavier.
In sum, I think these facts and considerations make it apparent that LCV use,
coupled with increases in weight limits due to NAFTA, for example, or the further
increase in multiple trip permits, will inevitably result in more bridge and pavement
damage because a given amount of cargo will be carried in fewer combinations.
Many LCVs, such as triples and Rocky Mountain doubles, rely on the use of short
trailers with single axles which are considerably more damaging to pavement than
the same amount of weight carried on tandem axles. Without either higher weight
limits or liberal permitting practices, LCVs are not economical alternatives to stand-
ard "eighteen wneelers." Furthermore, the use of LCVs at weights greater than
80,000 pounds is very advantageous to the trucking industry because of the shortfall
in user fee payments by these heaviest trucks when compared with the costs of re-
pairing bridge and pavement damage and what should be the trucking industry cost
responsibilities for this excessive damage.
Questions Asked by Senator Exon and Answers Thereto by Mr. Donaldson
longer-combination vehicles
Question. Is the data used for the conclusions drawn by Advocates sufficiently
adequate? Please provide the Committee with any recommendations by Advocates
for improvements in the data collection process.
Answer. As indicated in my previous response to question from Senator Exon,
there are manifold shortcomings in currently available data, including crash infor-
mation, on Longer Combination Vehicles (LCVs) which has forced investigators and
21 Truck Size and Weight User Fee Policy Analysis Study, Federal Highway Administration:
Sydec, Inc., March 1991.
'^^ Alternatives to Tax on Use of Heavy Trucks, Federal Highway Administration, January
1984.
*3 Managing the Use of Highway Pavements, Federal Highway Administration, n.d.
^See, e.g., Heavy Vehicle Cost Responsibility, Federal Highway Administration, Office of Pol-
icy Development, 1987.
^Overweight Vehicles — Penalties and Permits, Federal Highway Administration, 1993.
^Testimony of Thomas Donohue, President, American Trucking Associations, on the National
Highway System, March 3, 1994.
93
researchers to apply ingenious mechanisms to attempt the segregation of data cat-
egories for LCVs.None of these systems of interpretation are foolproof.
The Intermodal Surface Transportation Efiiciency Act (ISTEA) indicates in a
number of places Congressional intent to upgrade the accuracy and reliability of
truck data, including crash information. Part of the response to better data collec-
tion, especially for LCVs, is uniform, national use of the truck data format of the
National Governors Association (NGA). However, the NGA format cures a number
of shortcomings in previous data collection systems, such as the former Federal
Highway Administration (FHWA) 50-T self-reporting system but introduces sim-
plifying mechanisms that cannot provide the level of detail appropriate to tracking
relevant data categories for LCVs.
It is clear to me that an initiative to gather data that are specific to LCVs will
not occur through a voluntary national eftort but only if the FHWA mandates addi-
tional data collection elements for state execution. Given the agency's previous re-
sponse to unilaterally prescriptive requirements far the states, it is doubtful that
this can be achieved.
In the alternative, we believe that Congress should examine the potential of es-
tablishing specific data collection and analysis tasks for the new Bureau of Trans-
portation Statistics (BTS) created by Section 6006 of the ISTEA. Centralized data
collection requirements that would govern all surface transportation modal adminis-
trations would be beneficial in many ways. Given the joint administration of truck
data collection by the National Highway Traffic Safety Administration and the
FHWA, it could be advantageous to have the new BTS oversee the collection of new
data categories that could be used by both agencies for truck safety counter-
measures. In particular, LCV data categories on type of configuration, gross and
axle loads, road type, driver training and qualification, and other major features of