Truck Weight Limits Issues and Options -- Special Report 225 (1990) / Chapter Skim
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From page 11... ...
Executive Summ ary IN 1913 Maine, Massachusetts, Pennsylvania, and Washington became the first states to place limits on truck weight to protect highway pavements and bridges, and by 1933 all states had adopted a truck weight limit of some kind. The federal government entered this regulatory arena in 1956 by setting national truck weight limits for the Interstate highway system, which was then in its infancy.
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From page 12... ...
Tnucr W¡¡cHr Lurrs: lssurs ¡No OploNs The study focused on four issues identified in the study request that involve potential changes to these federal weight limits for interstate highways: . Elimination of existing grandfather provisions, ' Alternative methods for determining gross vehicle weight (GVw)
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From page 13... ...
Executive Summary (with consequent increases in air pollution and traffic congestion)
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From page 14... ...
Tnucx W¡lcnr Llulrs: lssurs RNo Oplorus reduction in the cost of goods movement by truck. This cost reduction would attract 23 million ton-miles of freight from rail to truck, representing a2.2 percent reduction in rail traffic.
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From page 15... ...
Executive Summary miles by 9 percent. This is about four times the 2.2 percent diversion from rail estimated by this study as a consequence of eliminating the g0,000-lb limit with no changes in length limits.
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From page 16... ...
Tnucx WelcHr Llptts: lssurs ,cNo Opt¡orus when the current bridge formula is applied to vehicles over g0,000Ib, one of the criteria used to develop the bridge formula-that the design stresses for HS-20 bridges not be exceeded by more than 5 percent-may be violated. For example, a long nine-axle combination truck carrying thä maximum weight permitted by the bridge formula can, depenäing on span length, exceed the HS-20 design stresses by as much as 12 percent.
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From page 17... ...
Executive Summary cause for these longer combinations the TTI formula is more restrictive than the current formula. TTI HS-20 Bridge Formula A modified version of the TTI formula was developed that keeps the 5 percent criterion for HS-20 bridges but drops the 3opercent criterion for H-15 bridges.
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From page 18... ...
Tnucx WrcHr Lrr¡lrs: lssurs ¡No OploNs . Other tandem axles, 30,000Ib for the tandem pair.
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From page 19... ...
Executive Summary Benefits of tractors with setback steering axles include better aerodynamics (which in turn provides better fueliconomy and reduced splash and spray) , improved maneuverability (because of a shorter wheelbase and sharper steering angles)
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From page 20... ...
10 TRucx W¡tcnr LrMtrs: lssuEs nNo OprroNs all four alternatives; however, there are practical problems for highway agencies in obtaining the revenues necessary to upgrade bridges. The Freightliner proposal, which could be implemented with any of the above four alternatives, was also found to have merit, but only if a steering-axle weight limit in the 12,000- to 14,000-lb range is included.
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From page 21... ...
Executive Summary lt Bridges (AASHTO 1993) , the operating rating is the absolute maximum permissible load level towhich a bridge may beiubjected.
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From page 22... ...
12 Tnucr WelcHr Lwrrrs: lssu¡s ¡No Oprorus some relief, in the form of either a libenlizationof the formula or a special permit program that would allow SHVs to exceed the formula, would be appropriate for vehicles that have difficulty operating under the current formula. Nonetheless, the committee finds the maximum weights proposed by NTWAC to be overþ permissive when applied with the relatively broad definition of SHV used for this study.
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From page 23... ...
TABLE ES-1 COST IMPACTS OF ALTERNATTVE SCENARTOS Change in Cost ($ billions/year) for Scenario Tiansport Pavements Bridges Grandfather Clause Elimination Uncapped Formula B NTWAC Froposal Canadian Interprovincial Limits TTI HS-20 Bridge Formula Uncapped TTI HS-20 Bridge Fìormula Combined,T.fI HS-2OÆorrrula B +7.8 -2.L -5.4 -71.7 -2.7 - 5.1 -5.2 -0.2 +0.0 +0.4 +0.5 -0.0 + 0.1 - 0.0 -0.3 +o.7 +3.0 +2.4 +0.3 +0.4 +0.9 +7.3 -7.4 -2.0 - 8.8 -2.4 -4.6 -4.3
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From page 24... ...
14 Tnucx Wetcur Llurrs: lssurs Rruo Optro¡.ls pavements and bridges) , followed by the Uncapped Tfl HS-20 Bridge Formula and the Combined TTI HS-20/Formula B scenarios.
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From page 25... ...
TABLE ES-2 OTHER IMPACTS OF ALTERNATTVE SCENARIOS Scenario Percent Change in Heavy Tiuck VMT Percent Change in Rail Ton-Miles Change in No. of Fatal Accidents/Year Grandfather Clause Elimination +3.2 -2.2 - 1.1 -6.3 -0.5 -2.2 -2.5 +0.8 -2.2 -0.9 -6.6 0.0 -2.5 -2.5 +350 -60 -40 -430 -40 -40 - 110 Uncapped Formula B NTWAC hoposal Canadian Interprovincial Limits TTI HS-20 Bridge Fonnula Uncapped TTI HS-20 Bridge Formula Combined TTI HS-2O/Formula B
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From page 26... ...
16 Tnucr Wscsl L¡rulrs: lssu¡s RNo Opr¡oNs In formulating the major recommendations for this study, the committee was guided by the following objectives: . To select, from the various proposed changes in truck weight regulations from industry groups and others, the most practical means to realize the productivity benefits of increased truck weights while reducing or eliminating possible adverse effects; ' To make changes in weight lirnits that would reduce truck accidents and encourage safety improvements in truck design and operation; .
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From page 27... ...
Executive Summary 17 with a permit program for vehicres over g0,000Ib and describes how the formula would be extended for these vehicles. Tiuck costs would decrease by $z.a birion per year ($2.7 billion per year in transport cost savings less $0.3 billion in irigheì taxes to coverpavemelt and bridge cost increases)
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From page 28... ...
18 Tnucx W¡cHr Llplts: lssues ¡¡lo OprtoNs cannot conveniently reach their destinations. Thus, if highway agencies posted rather than reconstructed many bridges, both truck cost savings and the added costs for bridges should be reduced.
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From page 29... ...
Executive Summary '19 140 120 |
From page 30... ...
TABLE ES-3 RECOMMENDED BRIDGE FORMULA LIMITS FOR AXLE GROUPS AxIeGroup Length(ft) Maximum Weight Axle-(kips)
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From page 31... ...
88.0 88.5 89.0 89.s 90.0 90.5 91.0 91.5 92.0 92.s 93.0 93.5 94.0 94.5 95.0 95.5 96.0 96.5 yt.o 97.5 52 53 54 55 56 57 58 59 60 61. 62 63 Ø 65 66 67 68 69 70 71 72.0 74.0 74.5 75.0 75.5 76.0 76.5 77.0 77.5 78.0 78.5 79.0 79.5 80.0 23 24 '25 26 n 28 29 30 31 32 33 34 35 36 90.s 91.0 91.5 y2.0 92.5 93.5 94-O 94.5 95.0 95.s 96.0 97.0 97.5 98.0 98.5 99.0 99.5 100.5 101.0 101.5 95.5 96.s 97.0 97.5 98.0 98.5 99.0 99.5 100.5 101.0 101.5 7V2.0 142.5 103.0 103.5 104.5 105.0 105.5 106.0 106.s 101.5 t42.0 102.s 103.0 103.5 104.0 104.5 105.0 106.0 106.5 107.0 107.5 108.0 108.5 109.0 109.5 110.5 111.0 111.5 112.0 87 88 89 90 91 92 93 94 95 96 n 98 99 100 L01 1V2 103 lM 105 105.5 106.0 106.5 107.0 107.5 108.0 108.5 109.0 109.5 110.0 110.5 111.0 111.5 r72.0 7L2.5 113.0 113.5 Lt4.O It4.5 111.0 111.5 112.0 112.5 113.0 113.5 L14.5 115.0 1.15.5 116.0 116.5 tL7.0 118.0 118.5 119.0 119.5 720.0 120.5 121.5 115.5 121,.0116.5 t2L.5t17.0 722.0117.5 122.5118.0 123.0118.5 124.0119.0 124.5119.5 t25.0120.5 125.512I.0 126.0127.5 126.5122.0 t27.0122.5 127.5723.0 t28.5123.5 129.0t24.5 t29.5L25.0 130.0125.5 130.5126.0 131.0 Ncrre:AxleGroupI-engthisthedistancebetweentheext¡emesofanygroupofthreeormoreconsecutiu"*
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From page 32... ...
22 Tnucx W¡rcHr Llulrs: lssu¡s ¡No Oplo¡ls permiß. Congress should enact legßløtion to authorize thß expanded role for FHWA.
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From page 33... ...
fxecutive Summary and enforcement costs due to the program, (e) a fee schedule for permits to 6e issued under the program by vehicle configuration and operating weight, (f)
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From page 34... ...
Tnucx W¡rcHr Lruns: lssurs nNo OprroNs by Congress, be operated in all states. For example, the LCVs that now operate at weights over 80,000Ib in those western states with grandfather exemptions to the federal gross weight limit could operate in any state that chose to establish a permit program for such vehicles.
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From page 35... ...
Executive Summary 25 nel requirements and other costs to enforcement agencies, and possible burdens on the trucking industry. fncreased enforcement would benefit highway agencies and highway users by decreasing the cost required to repair damaged pavements and bridges.
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From page 36... ...
lntroduction TRUCK WEIGIIT REGULATIONS generally are motivated by concern for protecting pavements and bridges from the effects of heavy loads. Pavement wear increases with axle weight and with the number of axle loadings to which the pavement is subjected.
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From page 37... ...
Tnucr W¡¡cur Lrvns: lssurs nHo OplloNs Finally, truck safety improvements can be required as a quid pro quo for more productive trucks. State legislatures have faced the task of balancing concerns for the highway system, trucking productivity, and safety since the first laws regulating truck weights were passed in 1913.
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From page 38... ...
Introduction 29 2. Alternative methods for determining vehicle weight limits; 3.
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From page 39... ...
TRUCK WErcHT Lr'lrs: lssu¡S Aruo Opttoxs 9, together with the cemmittee,s recommendations for changes in truck weight regulations and etforcement practices.
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From page 40... ...
2Development of State and Federal Truck Weight Regulations WITH THE PASSAGE OF THE L956 Highway Act, the federal government assumed a new role in funding and promoting Interstate highways. It offered 90 percent federal funding for Interstate highways through a Highway Trust Fund, which in turn was funded by a federal tax on gaJoüne, diesel fuel, truck tires, and other user fees.
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From page 41... ...
32 Tnucr Welcnr Llurrs: lssu¡s nNo OploNs assessed for road repair and maintenance, which they paid in the form of labor. As late as 1890, it was common for the voters of a county to ,,work out" their road taxes.
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From page 42... ...
Development of Weight Regu/ations 33 rutted dirt and mud roads. The cyclists joined forces with the National Grange, a populist farm movement founded in part because of farmer discontent with railroad pricing policies.
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From page 43... ...
34 Tnucx W¡rcHr Llutrs: lssuts ,qNo Oplo¡rs but recognized highway maintenance as a state responsibility, which, with limited exception, it has remained to this day. EARLY TRUCK WEIGHT LIMITS world war I boosted intercity trucking and forced many states to address truck weight regulations.
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From page 44... ...
Development of Weight Regulations 35 voluntary restrictions to the weight of vehicles (Bennett t921,, I2) .In order to give highway officials a maximum-weight vehicle to use in design, manufacturers agreed to limit the capacity of trucks so that the gross vehicle weight (GVW)
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From page 45... ...
Tnucr WacHr Lwrlrs: lssurs ¡No Opt¡oHs (AAlTTo)
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From page 46... ...
Development of Weight Regulations 37 to guarantee that damages would be repaired. one major limitation to the process of issuing permits was that movement over secondary or local highwuy.
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From page 47... ...
Tnucr Wercur Lr¡¡lts: lssurs ¡No Oprro¡rs This legislation also allowed operation on the Interstates of trucks with higherlimits thatwere legalin some statesbefore July L, 1956 (CBO 197g, 24) ; this was the first "grandfather clause." The 1956 act also called upon the U.S.
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From page 48... ...
Development of Weight Regulations Federal Bridge Formula In his 1964 report, the Secretary of Commerce recommended a table of permissible gross loads to protect bridges (Table 2-1)
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From page 49... ...
TABLE 2.1 PERMISSIBLE GROSS LOADS RECOMMENDED BY SECRETARY OF COMMERCE FORVEHICLES IN REGULAR opERATroN (u.s. secretar¡år-cãmleice u6a)
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From page 50... ...
3T 32 33 34 35 36 37 38 39 N 41. 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 59,000 62,500 60,000 63,500 64,000 64,500 65,500 66,000 66,500 67,500 68,000 68,500 69,500 70,000 70,500 71,500 72,W0 72,5N 73,500 74,000 74,500 75,500 76,000 76,500 77,500 78,000 78,500 79,500 80,000 67,500 72,500 68,000 73,000 69,500 74,000 69,000 74,500 70,000 75,000 70,500 75,500 71,000 76,00072,n0 77,ffi0 72,500 77,500 73,000 78,000 73,500 78,500 74,000 79,000 75,000 80,000 75,500 80,500 76,000 81,000 76,500 81,50077,5N 82,000 79,000 83,000 78,500 83,500 79,000 84,000 90,000 84,500 90,500 85,000 91,000 86,000 81,500 86,500 92,500 87,500 93,000 97,500 93,500 88,000 84,000 89,000 95,000 89,500 85,500 90,000 83,50094,500 90,00085,000 90,50085,500 91,00086,000 91,50086,500 92,00097,000 93,00087,500 93,50088,500 94,00089,000 94,50089,500 95,00090,000 95,50090,500 96,00091,000 96,5009L,500 97,50092,500 9g,ooo93,000 98,50093,500 99,ooo94,000 99,500 94,500 100,000 9s,000 100,500 95,500 101,000 96,500 102,000 97,000 102,500 97,500 L03,000 98,000 103,500 98,500 104,000 99,000 104,500 99,500 105,000 105,500 105,500 78,000 78,500 79,000 80,000 90,500 81,000 8L,500 82,000 82,500 83,500 94,000 84,500 95,000 95,500 86,000 87,000 87,500 88,000 88,500 89,000 89,500 90,500 91,000 91,500 92,000 92,500 93,000 94,000 94,500 100,500 Norn: The weights in this table are based on the formula ly : 500 [¿N(N - L)
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From page 51... ...
42 Tnucr Wrrcur Lwlts: lssu¡s ,cNo Oprrons vehicle with the same number of axles but only 30 ft between the extreme axles could only reach 66,500 lb. As noted above, Congress adopted the bridge formula in Lg74legislation but capped maximum weights at 80,000Ib.
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From page 52... ...
Development of Weight Regu/ations 43 Congress had requested that the states enforce laws against overloaded trucks when it increased maximum weight limits in1974.It required state governors to certify that they were adequately enforcing maximum weight limits and to provide data on truck weighing to the U.S. Secretary of Tlansportation.
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From page 53... ...
Tnucx WncHr Lrurs: lssurs RNo OproNs for single axles and 34,(Ð0lb for tandem axles, six states in the Mississippi Valley and Montana retained lower axle limits. As a iesult, truckers in interstate commerce were forced to operate at the lower limits or operate illegally.
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From page 54... ...
Development of Weight Regulations 45 EXCEPTIONS TO F'EDERAL LIMITS Grandfather Exemptions as Applied to Axle Limits As of January 1.988, there were 1l, states in which vehicles on Interstate highways could exceed the federal axle weight limits or gross weight limit without special permits (Table 2-2)
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From page 56... ...
New Jersey New Mexico New York North Carolina North Dakota Ohio Oklahoma Oregon Pennsylvania Rhode Island South Carolina South Dakota Tennessee Te¡ |
From page 57... ...
Tnucr WercHr Lrurrs: lssurs n¡ro OproHs with the bridge formula or may allow vehicle configurations, gross weights, and axle weights that do not comply with the bridge formula, such as in Massachusetts, New York, and Rhode Island. Permits are also granted for a single or for multiple trips.
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From page 58... ...
TABLE 2.3 STATUS OF LCV OPERATIONS IN }VESTERN STATES LCVs Permitted Rocky Mountain Double Tirnpike Double Triple Maximum Length(ft) Axle Limits (lb tbousands)
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From page 59... ...
50 Tnucr Wscnr Lrvrrs: lssurs RNo OplloNs ' Rocky Mountain doubles consisting of a tractor and two trailers-one typically 45 to 48 ft and the other typically Z7 to 28t/zft in length-which are permitted in 13 states; . Turnpike doubles consisting of a tractor and two trailers each up to 48 ft in length, which are permitted in nine states; and ¡ Tliples consisting of a tractor and three trailers, which are permitted in 10 states.
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From page 60... ...
Development of Weight Regu/atlons 51 bridge formula. Examples include lift axles that are lowered only when the vehicle is weighed by enforcement officials and dummy axles that can increase legal weight under the bridge formula by over 5,000 lb even though they carry very little weight themselves.
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From page 61... ...
52 Tnucx W¡rcHr LtMtrs: lssuEs AND OploNs The study found that if truck weight limits were increased, transport cost savings from improved trucking productivity could overwheknthe added costs for pavements and bridges. For example, the study found that increases in federal weight limits could reduce the nation's freight bill by about $4 billion per year.
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From page 62... ...
Development of Weight Regulations 53 The study found that allowing weights to be controlled only by existing axle load limits and the current bridge formula could severely overload existing bridges. To circumvent this problem, FHWA assumed that vehicle weights would be limited by the bridge overstress criteria used in developing the current bridge formula, rather than by the formula itself.
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From page 63... ...
54 Tnucr Wetcnr LrMtrs: lssuEs AND OploNs sumed that LCVs would be able to operate freely on a designated network of highways. WHI countered that this skewed the findings of the study by raising invalid safety concerns and argued that FHWA should have assumed that LCVs would continue to be subject to the special safetyrelated permits, rules, and regulations that the states already impose on these vehicles.
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From page 64... ...
Development of Weight Regu/ations 55 weather had also been sufficient to carry the maximum vehicle load. The states initially reacted to the effects of motor trucks by demanding the prohibition of vehicles that were too heavy for existing roads' Ultimately, however, they set limits and began designing roads that would accommodate them.
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From page 65... ...
56 Tnucr WncHr Lrurs: lssu¡s nxo OproNs axles and from 32,000 to 34,000Ib for tandem axles. Gross weights have increased from 73,280 to 80,000 lb, and twin trailer trucks (limited to 80,000lb)
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From page 66... ...
Development of Weight Regulations 57 GAO.
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From page 67... ...
3Trucking Productivity BACKGROUND INFORMATION ON THE EFFECTS of truck weight regulations on trucking productivity is given in this chapter and a description of the methods used to estimate the impacts of alternative truck weight regulatory scenarios on truck traffic, diversion to or from rail, and transport costs.l BACKGROT] ND The flexibility to choose vehicles and payloads that meet their needs effectively and at the lowest cost is of great economic value to motor carriers.
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From page 68... ...
Tnucr Wecnr L¡vtrs: lssues nNo Opnols Increases in truck weight limits increase the allowable weight per trip, so fewer trips and vehicle miles of travel are required to carry the same payload. Tiucks designed to operate at higher gross weights generally have higher empty weights and cost more to operate on a per-vehicle-mile basis.
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From page 69... ...
Trucking Productivity 61 . The 1995 forecasts of vehicle miles of travel (VMT)
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From page 70... ...
I -' ;.;_-;;; - rl_.; _ ;;;;.I rÈxas i Other Wesìern i .t t-9*
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From page 71... ...
ÏABLE 3-1 BASE-CASE VEHICLE MILES OF TRA\IEL, 1995 VMT (billions) by Region No.
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From page 72... ...
TABLE 3.2 BASE-CASE TON-MILES, 1995 Ton-Mles (billions) by Region No.
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From page 73... ...
Trucking Productivity All quantitative estimates were developed using a base case derived from FHWA forecasts of 1995 VMT by state, vehicle configuration, and highway functional class. Although the estimates were derived using foiecast 1995 traffic volumes, they actually were designed to represent the steady-state response of the industry to any change in weight limits; that is, they represent the situation that would exist in 1995 if the new limits had been in effect long enough for the industry to have acquired a fleet that had been optimized for operation under the new limits.
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From page 74... ...
Tnucx WrrcHr Lrulrs: lssu¡s ¡No Oprro¡rs as completely to the economic "model" used in this study for predicting responses to changes in weight limits. However, in the long run, comped: tive forces will result in productivity improvements in thJfor-hire sector that will force parallel changes in much of the private-carriage sector or will cause shifts in traffic to the for-hire sector.
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From page 75... ...
Trucking Productivity 67 . Extra costs of handling double vans in tightly constrained terminal areas; .
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From page 76... ...
68 Tnucr W¡rcnr Lrulrs: lssues ¡No OploNs for use at a specific GWV on the grades encountered) frequently determine the configuration of choice.
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From page 77... ...
Trucking Productivity interviewees expressed the opinion that special permit programs in the LCV states have resulted in significantly safer operations at higher weights and lengths. Interviewees also indicated that some shippers insist on carrying very high payloads in states with 80,000-lb limits, and that this is leading to the use of very lightweight equipment that reportedly has a shorter life and greater maintenance problems, and may be less safe.
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From page 78... ...
Tnucx W¡¡cur LrMlTs: lssuEs ¡No Opl¡or.ls where the traffic is and accept violations as a normal cost of operations. still others say they are forced to maintain mixed fleets becausË of access restrictions, although no instance of this was found among general freight truckload operators of dry vans.
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From page 79... ...
4Pavements THE EFFECTS OF HEAVY VEHICLES ON PAVEMENTS and the methods used in this study to estimate the effects of alternative truck weight regulatory scenarios on pavement costs are described in this chalter. The projections of pavement costs for individual scenarios are preiented in Chapter 8.
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From page 80... ...
Tnucx W¡¡cHr L¡urrs: lssurs ¡¡lo Oploxs The American Association of State Highway Officials (AASHO) Road Tþst conducted in the 1950s provided sets of ESAL values for single and tandem axles on various types of pavements.
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From page 81... ...
Pavements 73 AXLE WEIGHï (kips) FIGIJRE 4-1 Axle load effects on pavements: top, flexible pavements (structural number = 5, terminal serviceability : 2'5_)
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From page 82... ...
74 Tnucr W¡rc¡rr LrMrrs: lssu¡s n¡lo Oplor.ls OVERVIEW OF ANALYSIS METHODOLOGY The methodology used to estimate the impacts of alternative truck weight regulatory scenarios is described in detail in Appendix B This methodology consisted of three steps: 1.
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From page 83... ...
Pavements 75 grams were expanded so that there was no change in times between overlays and terminal serviceabilities. However, if resurfacing programs were not expanded, the maintenance workload could be much greater than it was before the increase in traffic.
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From page 85... ...
Pavemenß 0.26 v\= I I 33.6 68.6 181.3 316.4 325.7 307.0 285.6 L,5Ig.2 g tUJ t¡lJ O -L.
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From page 86... ...
(a) Three-Axle Single-Unit Truck Weight (lb 000s)
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From page 87... ...
(e) Six-Axle Tractor-Semitrailer (3-S3)
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From page 88... ...
Tnucr W¡rcHr Lllølrst lssurs ¡No OploNs offsetting part of the additional pavement wear caused by increased weight. To circumvent this problem, vehicles can be compared in terms of ESALs per unit of freight carried (Figures 4-4 to 4-7)
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From page 89... ...
100 100 0L 30 F :E o IIJÍ LL LL o |
From page 90... ...
500 400 300 200 100 0 t-I a IU tÍ, tL TL o Øozf, ofL zI J = U'J o IU 82 Tnucx WrrcHr Ln¿rrs: lssurs nruo OploNs 80 90 100 1 10 120 GRoSs VEHICLE WEIGHT (kips) fl^gu¡ry 1l- ¡S4þ_qer million pounds of freighr on rigid pavements: 3_S2,2-St-2,3-52-2, and 3-52-4 trucks.
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From page 91... ...
Pavemenß 83 have increased. A study by Bartholomew (1989)
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From page 92... ...
TABLE 4-3 SUMMARY OF REPORTED TRUCK TIRE PRESSURE MEASUREMENTS (Bartholomew 1989)
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From page 94... ...
86 TRUCK WErcHT LtMlTs: lssuEs AND OploNs Analysis of these data showed that taking wander into account reduced the adverse effects of single tires on pavement tryear, but that these effects were still significant (Figure 4-9)
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From page 95... ...
Pavemenß systems and truck configurations. Even less is known about their differential pavement wear effects.
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From page 96... ...
88 TRUcK WErcHT Llr¡lrs: lssu¡s AND OpnoNs with increases in pavement stiffness, the width of the single tire, and tire load.
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From page 97... ...
Pavemenß MDOH.
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From page 98... ...
5Bridges THE EFFECIS OF HEAVY VEHICLES ON BRIDGES and the methods used by this study to estimate the effects of alternative truck weight regulatory scenarioion bridge costs are discussed in this chapter.l ThJprojJctions of bridge costs for indivídual scenarios are presented id Chapter 8. BACKGROUND Of the 580,000 bridges in the United States, some 250,000 are listed as deficient in FH!
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From page 99... ...
92 Tnucr W¡rcHr Lrmrrs: lssurs n¡¡o OproNs and volumes, holvever, such strength reserves are being eroded and more bridges must be repaired, replaced, or posted for limited traffic. Loading demands on bridges include dead load (the weight of the bridge itself)
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From page 100... ...
Bridges 93 bution. This magnification of the legal loading is reflected in the safety factor, which is selected so that there is only a very small probability that a loading will be reached within the design life of a bridge that exceeds its strength capacity.
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From page 101... ...
TnucK WrrcHr Lr'¡rs: lssurs ¡¡lo Opr¡o¡¡s or design level. An inventory bridge rating is arrived at by selecting the most highly stressed bridge component and inserting the rating factor (RF)
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From page 102... ...
Bridges 95 Fatigue Life Bridge engineers must be concerned not only with overstress due to a singlé extreme loading event, but also with fatigue life considerations caused by repetitive loadings. Each truck crossing produces one.or more stress cyóles, which use up a portion of the component's total fatigue life.
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From page 104... ...
Bridges 97 longer spans, the H- and HS- models are supplemented by a uniform lane load, which better resembles a train of heavy vehicles. To account for heavier trucks in recent years, some states now design for HS-25 loads, which are 25 percent larger than the HS-20 loads.
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From page 105... ...
98 Tnucx W¡rcur Lrulrs: lssurs AND OpTtoNs These three vehicles were selected to closely match the federal bridge formula (also known as Formula B) for vehicles up to 80,000 lb.
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From page 106... ...
Bridges $53 billion replacement or upgrading cost. If a new truck weight regulation were intrãduced with higher loads, the number of bridges that cannot carry legal loads would inirease, thereby increasing the number of bridges that must be replaced, rehabilitated, or posted' Wîen a bridge is found to have inadequate load-bearing capacity to accommodate lãgal loadings, the owner of the bridge usually acts immeãiaæty to post tie bridgJ(to restrict its use to lighter vehicles)
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From page 107... ...
r00 Tnucx WrrcHr Lrutrs: lssugs AND OpÏoNs Replacement costs for existing bridges on primary and nonprimary highways were estimated by (a) specifying worst-case legar loadings under the base case and each alternative scenario, (b)
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From page 108... ...
Bridges 101 tee recommends this criterion for rating all bridges. Certainly there are many instances in which, because of traffic, bridge condition, and damage consequences, much more conservative stress levels should be used in rating for posting.
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From page 109... ...
102 Tnucx WercHr Lrmlts: lssu¡s ,qNo OpÏoHs order to estimate the effects of these exemptions on bridge fatigue costs. However, it was not possible to develop reliable estimates of these costs for several reasons: r Many states have had grandfather exemptions for over 20 years and have upgraded their bridges gradually to accommodate these vehicles.
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From page 110... ...
truck weights. A bridge is expected to have an economic life of at least 75 yeurs, unã during this period several cycles of new truck weighl regulations may occur.
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From page 111... ...
104 Tnucx Wscnr Lulrs: lssuts ¡No OploNs HS level, the assumptions made by this study in estimating costs for new bridges could result in an overstatement of these costs. The possibility that changes in truck weight regulations might increase fatigue-related costs for new bridges was also analyzed.
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From page 112... ...
Bridges 105 weights for shorter trucks when applied strictly to the Interstate system becãuse fewer than 1,000 of the 50,000 bridges on that system have design loads of H-15 or less. If the 30 percent overstress criterion for H-L5 bridges is dropped, the bridge formula could allow much higher weights for short trucks.
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From page 113... ...
106 Tnucr Wr¡crn LtMtrs: lssurs RtD Opno¡ls A,ASHTO.
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From page 114... ...
6SafeV and Traffic Operations CHANGES IN TRUCK WEIGHT REGULATIONS can affect highway safety and traffic operations by . Increasing or decreasing the amount of truck traffic, which in turn affects the number of accidents and highway congestion; .
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From page 115... ...
108 Tnucx WucHr Lrurrs: lssues ¡No Oplo¡rs vehicle simulations and track tests. Because of the controlled nature of these experiments, they are useful for in-depth examination of how truck weight and configuration may contribute to handling and stability, and thus how they may affect truck crashes.
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From page 116... ...
b 0) o o a, ã = 150 g 0'e o 0.8J or 0.7Ø ,ct 0.6 IF- o.sfr I 0.4 oj o.g ofr 0.2 Safety and Traffic Operations 109 \ - S-ale weslern doubles \ \ \ -_è 125 GROSS VEHICLE WEIGHT (kips)
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From page 117... ...
110 Tnucx Wscnr Lrurrs: lssues R¡¡o OprtoNs tion points and the flexibility of the trailer coupling worsens the rearward amplification problem for these vehicles (TRB 1986)
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From page 118... ...
Safety and Traffic Operations 111 equal, significant increases in GVW of existing five-axle doubles would increase the probabilities of their being involved in fatal rearward amplification-related crashes. Braking Two aspects of truck braking that affect traffic safety are stopping distance and vehicle control or stability during braking.
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From page 119... ...
112 Tnucx Wr¡cnr Lr'¡rs: lssurs ¡¡to Oprlo¡ts empty trailer behind a full one to facilitate trailer movement between terminals. Under such conditions, the wheels on the empty rear trailer can be severely overbraked (TRB 1986)
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From page 120... ...
Safety and Traffic Operations 113 Effect of Gross Weight The influence of GVW on steering sensitivity is of secondary importance relative to the influence of the variables mentioned above. Steering sensitivity of both existing tractor-semitrailers and five-axle doubles decreases slightly with increased GVIV (Figure 6-3)
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From page 121... ...
114 Tnucx Wrcnr LrMrrs: lssuEs ¡No Oprto¡rs the rear wheels may fall off the pavement, or the trucks may sideswipe roadside objects. Effect of Tluck Configuration Low-speed offtracking of existing five-axle doubles with 28-ft trailers is abottT percent lower than that of 45-ft tractor-semitrailers (Fancher et al.
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From page 122... ...
Safety and Traffic Operations 115 1.0 -- ¿' -- tfactor-semitrailers I I I 75 100 GROSS WEIGHT (kips)
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From page 123... ...
116 Tnucx W¡rcHr Lrurs: lssurs AND OploNS of the lead unit and lateral forces are not propagated forward through the coupling between the second and first trailer.
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From page 124... ...
Safety and Traffic Operations 117 namic resistance, drive-train-to-gear ratios, tires, and (most important) weight-to-horsepower ratio (gross weight divided by net horsepower)
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From page 125... ...
118 Tnucr W¡rcnr Lru¡rs: lssu¡s Rr.ro OproNs may become inadequate. Hutchinson (1988)
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From page 126... ...
Safety and Traffic Operations 119 established between truck accident rates and the ease of freeway maneuvers, or truck length, or the weight-to-horsepower ratio. AASHTO's guidelines for the length of acceleration lanes on freeways are based on the performance characteristics of passenger cars.
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From page 127... ...
120 Tnucx Wrrcur Lrurrs: lssurs nxo Oprrons 1981)
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From page 128... ...
-- - 400 lb/net HP - 300 lb/net HP .- 200 Ib/net HP - AASHTO cars '4'' /// ./ -- 'ê'¿" 3000 Þ uJoz f; zooo U) o l:c(5 õ 1000 Safety and Traffic Operations 121 DESIGN SPEED ON MAJOR HIGHWAY (mph)
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From page 129... ...
122 Tnucx Wercgr Lr¡¡rrs: lssues ¡¡ro Oprro¡rs on upgrades. Tiuck traction ability improves as the percent of GWV on the tractor drive axles (or traction ratio)
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From page 130... ...
Safety and Traffic Operations 123 Effect of Tluck Configuration Combination vehicles are rnore likely than single-unit trucks to experience rollover after hitting a longitudinal barrier. Effect of Gross Weight Highet truck gross weights and higher centers of gravity may adversely affect the ability of longitudinal barriers tô restrain and redirect trucks.
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From page 131... ...
124 fRucr W¡cHr LtMtrs: lssuEs AND OploNs ACCIDENT RATES AND SEVERITY Determining the effects of t¡uck weight and configuration on accidentrates is very difficurr-because rh";; r"f; "re also highly sensitive ro driverand environmenral facto¡s. Th;;fi;;r" "ttributablî iä rrïrï^*
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From page 132... ...
Safety and Traffic Operations 125 develop programs to reduce accident losses. That study is attempting todefine a national monitoring ry*
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From page 133... ...
126 Tnucx WrrcHr LrM¡rs: lssues nND OpÏo¡.rs TABLE 6,2 FHXAL AççlqENT RArES OF STNGLE-UNrT TRUCKS,TRACT'R"SEMTTRATLERS,AND-ó-oîni-esicãñõuáì'åi"i.ìisïi' Vehicle 1985 VMT' (millions) 1980-1984 FatalInvolvements 1985 Fatal Involvement Rateà (Involvement/ 100 million vMT)
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From page 134... ...
Safety and Traffic Operations 127 odological-flaws (TRB 1986; FFIwA 1987; Jovanis et at. 19g9; stein andJones 1988)
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From page 135... ...
ffi"?
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From page 136... ...
Safety and Traffic Operations 129 cles on limited-access highways and other roads are shown in Figures 6-6 to 6-9. These data suggest a moderate increase in accident rates for higher gross weights, although the relatively small number of data points and high degree of scatter make drawing conclusions from these data difficult.
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From page 137... ...
o 1.5 lÉ. Þ it 1'o uJ J9 o.s II I rrl I <35 35-50 50-60 6H5 65_70 70_75 7$_80 >80 GROSS VEHICLE WEIGHT RANGE (kips)
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From page 138... ...
Safety and Traffic Operations 131 FIGURE 6.9 Fatal accident involvement ratios: single-unit trucks on other roads. Involvement ratio : (percent involvemenUpercent travel)
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From page 139... ...
132 Tnucx Wecur LtMrs: lssuEs RNo Oprro¡rs accidents (the proportion of total truck accidents that are fatal, nonfatal iniyy' and property damage only with no injuries) is not significantlyinfluenced by truck gross weight or configuration.
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From page 140... ...
Safety and Traffic Operations 133 . Without making changes to truck dimensions, number of axles, and vehicle and component designs, increased truck weights would increase accident involvement rates of trucks, particularly for rollover and ramprelated crashes for all trucks, and in rearward-amplification-related crashes for multiple-trailer combinations.
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From page 141... ...
134 Tnucr WrrcHr Llutts: lssurs ¡¡ro Oplo¡rs Final Report. Bureau of Motor Carrier Safety, FHWA, U.S.
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From page 142... ...
7Enforcement of Tiuck Weight Limits ENFORCEMENT IS A CRITICAL ELEMENT of any plan for controlling vehicle weights. rilithout effective enforcement, including the certainty of penalties and sanctions sufficient to deter violation, weight limit laws become meaningless.
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From page 143... ...
136 Tnucr WercHr Lrulrs: lssuEs ¡uo Oprro¡rs act required states to certify that they are enforcing weight limits on federal-aid highways. The 1978 highway act strengthened this provision by authorizing the U.S.
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From page 144... ...
Enforcement 137 TABLE 7-1 ENFORCEMENT OF VEHICLE WEIGHT LIMITS: USE OF SCALES (FHWA 1989)
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From page 145... ...
138 Tnucx Wrrcnr Llulrs: lssu¡s AND OploNS guilty without good reason, suspend all or most of the fine, or simply refuse to impose the statutory fine.
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From page 146... ...
Enforcement 139 ment, truck overloading did not decrease significantly between 1,9g4 and 1987 (FHWA 1989)
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From page 147... ...
140 TRUCK WErcHT LIMITS: IssUEs AND OPTIoNS ECONOMIC INCENTIVES FOR ILLEGAL OVERLOADING fn some states, the combined effect of low probability of apprehension and low fines provides a strong economic incentive for illegal overloading. This may be illustrated by the following examples: .
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From page 148... ...
Enforcement 141 violate the law. Accordingly, the American Tiucking Associations, the National Tiuck Weight Advisory Council (NTIVAC)
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From page 149... ...
142 Tnucr WrrcHr Lrr',rts: lssurs nNo OploNs POSSIBLE CONGRESSIONAL ACTION The committee identified several actions that congress should consider as a means for improving the enforcement of truck weight laws. These actions are presented as options for further study rather than recommendations, because the committee has not investigated their advantages and disadvantages in depth.
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From page 150... ...
Enforcement 143 those who are responsible for placing overweight shipments in the stream of interstate commerce. This would require the ability to reach those responsible for overloading ocean transport containers or to prevent the inland movement of overweight containers via commercial motor transport.
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From page 151... ...
144 Tnucr Wrrcnr Lrurrs: lssurs ¡No Oplo¡rs REFERENCES ABBREVIATIONS DOT U.S. Department of Tlansportation FHWA FederalHighwayAdministration DOT.
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From page 152... ...
Blmpacts of Proposed Changes in Truck Weight Regulations THE ESTIMATED IMPACTS OF VARIOUS PROPOSALS for changes in truck weight regulations that have been advanced by the trucking industry, highway agencies, and other groups are reviewed in this chapter. Impact categories examined by the committee include costs to highway agencies for pavements and bridges, and highway safety and transport costs.
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From page 153... ...
146 TRUCK WEtcHT Lrrr¿rrs: lssu¡s RNo Oprro¡rs 6. TTI HS-20 Bridge Formula: modified version of the TfI formula that would allow higher weights on single-unit trucks and shorter combination vehicles.
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From page 154... ...
lmpacß of Proposed Changes '147 industry groups and none were judged by the committee to offer significant advantages over the alternatives selected by the committee for study. IMPACT ANALYSIS METHODOLOGY The methods used to estimate the impacts of alternative truck weight regulation scenarios on trucking productivity, pavements, bridges, and highway safety are described in Chapters 3, 4,5, and 6, respectively.
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From page 155... ...
148 Tnucx WercHr Lrulrs: lssues nxo OploNs The committee also considered the possibility that a reduction in truck costs could produce an additional increase in truck freight by stimulating demand for goods movement. However, the committee concluded that this effect would be very small relative to the increase in truck freight due to diversion from rail, and that explicitly incorporating this effect would not significantly alter the impacts of alternative scenarios.
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From page 156... ...
Impacß of Proposed Changes 149 Safety impacts for each scenario were estimated using (a) the accident rates (by vehicle type and operating weight)
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From page 157... ...
1s0 Tnucx W¡tcnr Llufs: lssurs ¡No OplloNs date these vehicles. Because the primary motivation for eliminating grandfather exemptions would be to reduce costs to highway agencies, a pgticy of eliminating grandfather exemptions on Interstate highways while allowing states to keep higher limits on non-Interstate highways would be counterproductive.
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From page 158... ...
lmpacß of Proposed Changes t 5't six-axle twins..It was assumed that under this scenario all freight currently carried in double trailer and truck-trailer combinations with more than six axles would be carried by five- or six-axle tractor-semitrailers (although some truck-trailer movements might actually be diverted to single-unit trucks)
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From page 159... ...
TABLE 8.1 EFFECTS OF GRANDFATTIER CLAUSE ELIMINATION SCENARIO ON TRUCKACTTVITY Change in VMT/Yea¡ by Ttuck Tlpe Single-Unit Combination Due to change in vehicle use Due to diversion to rail Total +0.70 0.00 +0.70 +4.5 0.0 +4.5 +3.85 -0.40 +3.45 +3.4 -0.4 +3.0 +4.55 -0.40 +4.15 +3.4 -o.4 +3.0
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From page 160... ...
TABLE 8-2 EFFECTS OF GRANDFATHER CLAUSE ELIMINATION SCENARIO ON TRANSPORT COSTS Change in Tlansport Costs ($ 1988 billions) Single-Unit Tirucks Combination Tiucks Total Effect Dollars Percent Dollars percent Dolla¡s p*
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From page 161... ...
154 Tnucx Wgcnr Llvlts: lssurs nNo OploNs Table 8'3.3 For single-unit trucks, the largest estimated impact (14.0 percent) is for the Middle Atlantic region, in which all stateJ curently allow operation of single-unit trucks at high weight limits.
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From page 162... ...
TABLE 8-3 EFËECTS OF GRANDHATHER CLAUSE ELIMINATION SCENARIO ON TRUCK COSTS BY REGION Region Change in Tiansport Costs ($ 1988 millions) Single-Unit Tlucks Combination Tiucks Total Dollars" Percent Dollars" Percent Dollars' Percent New England +273 +5.4 +80 +2.0 +353 +3.9 (Conn., Maine, Mass., N.II., R.I., Vt.)
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From page 163... ...
156 Tnucr Wucnr L¡vms: lssurs ¡No Oploxs crete and asphalt, that are normally transported in single-unit trucks, a 35 percent increase in truck costs could be quite significant, but for the other commodities, such an increase would usually represent only 1 to 3 percent of the value of the product. The impacts of inc¡eased costs would generally depend on the type of market in which a commodity was sold.
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From page 164... ...
lmpacts of Proposed Changes 157 haul from the farm is usually relatively short and is almost always made by truck. Subsequent hauls are generally much longer and may be made by truck, rail, or barge.
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From page 165... ...
158 TRUCK WEcHT Lttr¿lrs: lssu¡s Rto OploNs Favement and Bridge Costs The elimination of grar¡dfather exemptions would reduce pavement and bridge costs; however, these cost savings are small relative to the increase in truck costs (Table 8-4)
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From page 166... ...
lmpacß of Proposed Changes 159 Accidents The scenario would result in more accidents because of the increased number of vehicles required to carry the same payload. The number of accidents on the nation's highways would increase by 28,910 per year' including 350 more fatal accidents, 8,360 more injury accidents, and 20,200 more accidents that result in property damage.
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From page 167... ...
160 Tnucx WHcHr Lrurrs: lssurs ¡No OprroNs mix of commodities normally carried by a given trailer, and other operational considerations. Lifting the GVW limits would result in substantial increases in the use of doubles and six-axle tractor-semitrailers.
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From page 168... ...
lmpacß of Proposed Changes 161 commodity and operational characteristics. For commodities carried in hoppers or dry bulk tankers, the preferred configuration would nearly always be a heavy double (that is, a seven-, eight-, or nine-axle double)
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From page 169... ...
162 Tnucr WrrcHr Llulrs: lssu¡s RNo Oplorus more difficult pickup and deliveryproblems with twin vans may limit their use in many truckload operations. Accordingly, eliminating the g0,000-lb GVw cap is estimated to result in shifts from five-axle 4g-ft vans to both six-axle vans and five-axle twins.
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From page 170... ...
lmpacß of Proposed Changes 163 TABLE 8-5 EFFECTS OF UNCAPPED FORMULA B SCENARIO ON TRUCK ACTIVITY Change in VMT/Year by Combination Tiucks Billions Percent Due to change in vehicle use Due to diversion from rail Total vehicle-mi.7 The diverted traffic represents about 2.2 percent of base-case rail traffic and 1.3 percent of ton-miles carried by combination trucks. six-axle tractor-semitrailers are expected to account for about half (16.80 billion)
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From page 171... ...
164 Tnucx W¡lcHr LrMtTs: lssuEs ¡No Opttors TABLE 8-6 EFFECTS OF LINCAPPED TRANSPORT COSTS FORMULA B SCENARIO ON Costs Effect Dollars (1988 billions) Percent T?
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From page 172... ...
lmpacß of Proposed Changes 165 TABLE 8.7 UNCAPPED FORMULA B SCENARIO IMPACT SUMMARY Tlpe of Impact Change per Year 1995 truck miles (millions) Single-unit trucks (3 + axles)
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From page 173... ...
166 Tnucx W¡¡cur L¡vlts: lssurs ¡No Oploxs which these bridges are located could be used by the heavier trucks that would operate under this scenario. These practical considerations suggest that if this scenario were to be implemented, it should be limited, at least initially, to Interstates and other highways on which most existing bridges can already accommodate the heavier vehicles.
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From page 174... ...
Impacß of Proposed Changes 167 materials, and building materials and supplies, has proposed that any state, regardless of whether it qualifies for grandfather exemptions from the federal requirements, should be able to issue permits for SHVs, including dump trucks, solid-waste compactor trucks, ready-mix concrete trucks, and other trucks with short wheelbases and specialized equipment for handling heavy loads. Under the NTWAC proposal, an SHV would be exempt from federal gross and axle weight limits and the bridge formula.
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From page 175... ...
168 Tnucx W¡rcHr Lwrrrs: lssurs nxo OploNs loads did not exceed the operating rating of the bridges over which the vehicle would travel. To assist this study in specifying a scenario based on their proposed permit program, NTWAC suggested the following definition of an SHV for the purposes of the study: a single-unit or combination truck with at least three load-bearing axles that .
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From page 176... ...
lmpacts of Proposed Changes 169 Under the NTWAC Proposal Scenario, virtually all single-unit and combination concrete mixers and garbage haulers, single-unit dump trucks with three or more axles, and dump-trailer combinations could eventually be replaced by vehicles designed for operation at the SIIV weight limits. Applying the scenario definition of an SHV to the truck populations reported in the 1982 Tluck Inventory and Use Survey, 176,000, or 46 percent, of all single-unit trucks with three or more axles and 87,000, or 6 percent, of all combinations could qualify as SHVs.
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From page 177... ...
170 Tnucx W¡lcHr LrMtts: lssu¡s Rruo OprroNs ings and a moderate shift from three-axle to four-axle trucks are expected to reduce use of three-axle trucks and increase use offour-axle trucks. A nef reduction of 900 million vehicle-mi is expected, which represents a 5.g pgrcent reduction in vMT of single-unit trucks (Tilble g-g)
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From page 178... ...
TABLE 8-8 EFFECTS OF NTWAC PROPOSAL SCENARIO ON TRUCK ACTIVITY Change in VMT/Year by Tiuck Tlpe Single-Unit Combination Effect Billions Percent Billions Percent Billions P.ercent Due to change in vehicle use -0.90 -5.8 - 1.00 -0.9 - 1.90 - L.5 Duç to diversion from rail 0.00 0.0 +0.47 +0.4 +0.47 +0.4 Total -0.90 -5.8 -0.53 -0.5 -1-43 - 1.1
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From page 179... ...
TABLE 8-9 EFFECTS OF NTWAC PROPOSAL SCENARIO ON TRANSPORT COSTS Change in Tiansporr Costs ($ 198g billions) Single-Unit Tlucks Combination Tiucks Total Effect Dollars Percent Dollars Percent Dollars Percent Tiuck costs Due to change in use Due to diversion from rail Total Logistics costs Railroad costso Total -4.55 0.00 -4.55 0.00 0.00 -4.55 - 5.1 - 5.1 - 0.86 +o.52 -0.7+0.4 -5.47+0.52 -4.89 -0.23 - 0.31 -2.6 +0.2 -2.3 - 0.3 - 1.0 - 0.34 -0.23 - 0.31 -0.88 -0.3 -0.3 - 1.0 -5.43 " Competitive rate decreases by railroads would reduce shipper costs by an additional $0.09 biltion *
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From page 180... ...
Impacß of Proposed Changes 173 TABLE 8-10 NTWAC PROPOSAL IMPACT SUMMARY Type of Impact Change per Year 1995 truck miles (millions) Single-unit trucks (3+ axles)
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From page 181... ...
174 Tnucr W¡rcnr Lrurrs: lssu¡s ¡No Oplo¡ls carry the same amount of freight in less than half the number of trips, its pavement impact would be much greater than the Formula B truck. The NTWAC proposal would increase the number of load-deficient bridges by 53,000 on primary highways and L14,000 on nonprimary highways.
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From page 182... ...
lmpacß of Proposed Changes 175 spread noncompliance could lead to the loss of political support for the permit program. Further, the threat of having their permits revoked would provide incentives for individual firms not to violate the terms of the permits.
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From page 183... ...
DIMENSIONS WE¡GHTS Overall Length(m 75.5 tl) MAXIMUM GROSS COMBINAT¡ON WEIGHTS 3 ales: 56.9 kþs 4 axl6s: 75.9 kþ3 5 axlss: 94.9 kþs 6 ales: 111.7 kips Single Axlo: lH 21.9 kips Tmdem Axle: nux 40.8 kiPs TlHsm Axl€: mar 57.7 kips FIGURE 8-1 Canadian interprovincial limits for 1988)
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From page 184... ...
MENSIONS Ovorall Length (rnax 75.5 ft) Box Length(rEx 60.7 ft)
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From page 185... ...
DIMENSIONS Axle Spræd Tandem: min 3,9 ft, lu 6.1 lt 'lnlerale spacing: Single-single, nin 9.8 fl Single-tadem, min 9,8 ft Tandem-landem, min 16.4 ft Ta¡lden¡-tridm, min 18.0 tl WEIGHTS Tadsm: min 3.9 fl, max 6.1 fl lntårãle (rä æ.3 lt) Single Axle: md 21.9 kips Tadem Axle: md 40.8 kips Tmdem Axle: mu 40.8 kips Tridem Axle: mu 55.3 kips Pverall Lenglh(ffi 75.5 ll)
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From page 186... ...
lmpacß of Proposed Changes 179 scenario on use of single-unit trucks were derived by modifying the singleunit payload ton-mile distributions used in the NTWAC Proposal Scenario to allow for lower weight limits and the expected greater use of fouraxle trucks for weight-limited traffic. The procedure presumes no reduction in current operation of single-unit trucks at weights above 54,000 and 71,000 lb in states where operation at such higher weights now occurs either legally or illegally.
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From page 187... ...
180 Tnucx Wrrcnr Lu¡rs: lssurs ¡No Opro¡ls cost of tank trailers, the phase-in period for new equipment would be appreciably longer than for other trailer types. Flatbed operators are expected to shift to B-trains wherever practical, with six-axle tractor-semitrailers being used for loads requiring longer trailers and for access to locations where twins are not allowed.
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From page 188... ...
lmpacß of Proposed Changes 181 or 4.5 percent of annual VMT of single-unit trucks with three or more axles (Table 8-11) , and transport costs for use ofthese vehicles is expected to decline by $3.34 billion, or 3.7 percent (Thble 8-12)
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From page 189... ...
TABLE 8.11 EFFECTS OF CANADIAN INTERPROVINCIAL LIMITS SCENARIO ON TRUCK ACTTVITY Change in VMT/Year by Truck Type Single-Unit Combination Billions .Percent Due to change in vehicle use Due to diversion from rail Total -0.70 0.00 -0.70 -4.5 0.0 -4.5 - 10.10 +2.77 -7.33 -9.0 +2.5 -6.5 - 10.80 -8.5 +2.77 +2.2 - 8.03 -6.3
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From page 190... ...
TABLE 8-] .2 EFFECTS OF CANADIAN INTERPROVINCIAL LIMITS SCENARIO ON TRANSPORT COSTS Change in Transport Costs ($ L988 billions)
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From page 191... ...
184 Tnucx W¡rcnr'Lrtvlts: lssurs Ruo Oplorls TABLE 8.13 CANADIAN INTERPROVINCIAL LIMITS SCENARIO IMPACT SUMMARY Type of Impact Change per Year 1995 truck miles (millions) Single-unit trucks (3 + axles)
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From page 192... ...
lmpacß of Proposed Changes 185 The Canadian Interprovincial Limits Scenario would increase the number of load-deficient bridges by 32,000 on primary highways and 67,000 on nonprimary highways. If all 99,000 additional load-deficient bridges were replaced, total bridge costs would increase by $2.4 billion per year under this scenario.
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From page 193... ...
186 Tnucx WrcHr L¡r'¿rrs: lssu¡s AND OploNs The TTI formula and the current bridge formula are compared in Figure 8-4. The TTI formula generally allows slightly higher weights on single-unit trucks and short combinations.
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From page 194... ...
lmpacts of Proposed Changes "t87 change significantly under their formula, productivity would improve slightly, but pavement impacts could be slightly worse. TTI HS.2O BRIDGE FORMULA As part of their study for FHWA, TTI also developed a modified version of Equation 1.
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From page 195... ...
188 TRucr WrcHr Lrpurs: lssues nno Oplroxs law provides a temporary exemption from Formula B for those shorter tractor-semitrailers that would otherwise be greatly affected by the difference between the two formulas. Specifically, the law allows motorvehicles hauling tank trailers, dump trailers, and ocean transport containers to operate with 68,000Ib on two consecutive sets of tandem axles, provided the spacing between the first and last axles is 30 ft or more.
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From page 196... ...
Impacts of Proposed Changes 189 advantage over three-axle trucks, resulting in a substantial shift in VMT from three-axle to four-axle trucks. The 600 million vehicle-mi reduction in use of single-unit trucks noted previously is the net effect of a 3.39 billion drop in VMT of three-axle trucks and a 2.79 billion increase in VMT of four-axle single-unit trucks.
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From page 197... ...
190 Tnucx Wrrcnr Lwurs: lssu¡s RNo Oprro¡rs TABLE 8-16 TTI HS-20 BRIDGE FORMULA SCENARIO IMPACT SUMMARY Type of Impact Change per Year 1995 truck miles (millions) Single-unit trucks (3+ axles)
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From page 198... ...
lmpacß of Proposed Changes 191 In the case of combinations, it is appropriate to compare the Uncapped Til HS-20 Bridge Formula Scenario with the Uncapped Formula B Scenario. Under the former, five- and six-axle rigs would be allowed to operate at weights that are slightly higher than those allowed under Formula B , whereas under the latter, weight limits for rigs with more axles would be lower.
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From page 199... ...
TABLE 8-17 EFFECTS OF UNCAPPED TTI HS-20 BRIDGE FORMULA SCENARIO ON TRUCK ACTTVITY Change in VMT/Year by Ttruck T-ype Single-Unit Combination Due to change in vehicle use Due to diversion from rail Total -0.60 0.00 -3.9 0.0 - 3.9 -3.36 + 1.13 -2.23 -3.96 + 1.13 -2.83-0.60 - 3.1 +0.9 -')
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From page 200... ...
lmpacts of Proposed Changes 193 The distribution of the changes in vMT across axle configurations is appreciably different from that under uncapped Formula B under the úncapped TfI HS-20 Bridge Formula Scenario, six-axle tractor-semitraileiJ are expected to account for about two-thirds of the increase in VMT of larger combinations, with the remainder being split almost equally between six-axle doubles and five-axle doubles.
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From page 201... ...
TABLE 8-18 EFFECTS OF UNCAPPED TTI HS-20 BRIDGE FORMULA SCENARIO ON TRANSPORT COSTS Change in Tiansport Costs ($ 1988 billions) Single-Unit Combination Tiucks Trucks Total Effect Dollars Percent Dollars Percent Dollars percenr ïiuck costs Due to change in use -2.73 -3.0 -2.27 -1.9 -5.00 -2.4Due to diversion from rail 0.00 + 1.39 +1.2 + 1.39 +0.7 Total Logistics costs Railroad costso Total -2.73 -3.0 -0.88 -0.7 -3.61 _1.7 0.00 0.00 - 0.6s -0.85 -2.38 _0.65 -2.8 -0.85 -2.8 - s.11 -2.73 " Competitive rate decreases by railroads would reduce shipper costs by an additional $0.24 billion under this scenario.
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From page 202... ...
lmpacts of Proposed Changes 195 Pavement and Bridge Costs Pavement costs under the Uncapped TTI HS-20 Bridge Formula Scenario would increase by $1,40 million per year (Table 8-19)
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From page 203... ...
196 Tnucr W¡rcHr L¡vns: lssues ¡No Oploxs worse than a five-axle tracto¡-semitrailer at 80,000 lb. If the scenario were modified so that five-axle doubles were not allowed to operate over g0,000 lb, pavement impacts would be sharply reduced.
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From page 204... ...
lmpacß of Proposed Changes 197 (Figure 8-5 and Table 8-20)
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From page 205... ...
TABLE 8-20 COMBINED TTI HS-20IFORMULA B SCENARIO: MAXIMUM WEIGFIT FOR AXLE GROUpS Maximum Weight (kips) 5-678Axles Axles Ales AxleGroup Length (fÐ 5-678Ales Axles Axles AxleGroup Length (fÐ AxleGroup Length(ft)
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From page 206... ...
72.0 74.0 74.5 75.0 75.5 76.0 76.5 77.0 77.5 78.0 78.5 79.0 79.5 80.0 23 24 25 ? Á n a3 29 30 3L 32 JJ 34 35 36 52 53 54 55 56 57 58 59 60 6t 62 63& 65 66 67 68 69 70 77 88.0 88.5 89.0 89.5 90.0 90.5 91.0 91.5 92-0 y2.5 93.0 93.5 94.0 94.5 95.0 95.5 96.0 96.5 n.0 v7.5 gt 88 89 90 9L v2 93 94 95 96 n 98I 100 101 702 1.03 704 105 105.5 L06.0 106.5 107.0 107.5 108.0 108.5 109.0 109.5 110.0 110.5 111.0 11L.5 112.0 1t2.5 113.0 1.13.5 7't4.0 114.5 111.0 111.5 112.0 1L2.5 113.0 113.5 L74.5 115.0 115.5 116.0 1,1,6.5 1t7.0 118.0 118.5 119.0 119.5 t20.0 120.5 121.5 90.5 91.0 91.5 v2.o y2.5 93.5 94.0 94.5 95.0 95.5 96.0 y7.0 97.5 9s.o 98.5 99.0 99.5 100.5 101.0 101.5 95.5 96.s n.0 97.5 98.0 98.5 99.0 99.5 100.s 101.0 101.5 \U¿.0 1V2.5 103.0 103.5 104.5 105.0 105.5 106.0 106.5 101.5 1U2.0 702.5 103.0 103.5 104.0 104.5 105.0 106.0 106.5 1U7.0 L07.5 108.0 108.5 109.0 109.5 110.5 L11.0 111.5 LLz.O 115.5 I2t.0116.5 121,.5117.0 722.0117.5 122.5118.0 123.0118.5 724.0119.0 124.5119.5 125.0t20.5 125.5721.0 126.0 121..5 126.5122.0 7n.0122.5 127.5123.0 128.5123.5 129.0724.5 129.5\25.0 130.072s.5 130.5126.0 131.0 Norr; A¡le Group l"ength is the distance befween the extre-mes_of atry group of th¡ee or more co*
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From page 207... ...
TRUCK WErcHT LtMtrs: lssuEs AND OploNs lesser extent, six- and seven-axle twins more attractive under the Combined TTI.HS-20/Formula B Scenario than under the Uncapped Formula B Scenario and would make somewhat greater use of these three configurations and somewhat less use of eight- and nine-axle twins. Under the Combined TTI HS-20/Formula B Scenario, annual VMT by three- and four-axle single-unit trucks is expected to decline by about 600 million vehicle-mi (3.9 percent)
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From page 208... ...
TABLE 8-21 EFFECTS OF COMBINED TTI HS-20/FORMULA B SCENARIO ON TRUCK ACTIVITY Chånge in VMT/Year by Truck Tþe Single-Unit Combination Percent Due to change in vehicle use Due to diversion from rail Total -0.60 0.00 -0.60 -3.9 0.0 -3.9 -3.74 +1.74 -2.6L -3.3 + 1.0 -2.3 -4.34 +1.74 -3.21 -3.4 +0.9 -2.5
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From page 209... ...
TABLE8.Z2 EFFECTS OF COMBINED TTI HS-2OIFORMULA B SCENARIO ON TRANSPORT COSTS Change in Tlansport Costs ($ 1988 billions) Single-Unit Tlucks Combination Tiucks Total Effect Dollars Percent Dollars percent Dollars percent Tiuck costs Due to change in use -2.73 -3.0 -2.40 -2.0 -5.13 -z.sDue to diversion from rail 0.00 +1.41 +1.2 +1.41, +A.7 Total Logistics costs Railroad costs" Total -2.73 - 3.0 - 0.99 _ 0.8 _3.72 _ 1.8 0.00 0.00 -2.73 -0.66 -0.66 -0.86 -2s -0.86 _2.9 -2.51 -5.U o competifive rate decreases by railroads would reduce shipper costs by an additional $0.24 billion under this scenario.
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From page 210... ...
lmpacß of Proposed Changes 203 TABLE 8-23 COMBINED TTI HS-2O/FORMULA B SCENARIO IMPACT SUMMARY Type of Impait Change per Year 1995 truck miles (millions) Single-unit trucks (3+ axles)
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From page 211... ...
204 Tnucx W¡rcsr Lrurrs: lssurs RNo OproNs (rather than replace) many bridges, particularly on low-volume routes.
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From page 212... ...
lmpacß of Proposed Changes 205 ' If the 80,000-lb limit were eliminated, five-axle doubles could operate under Formula B and current axle weight limits of up to 92,000 lb(assuming a practical maximum steering-axle weight of i2,000 iu an¿ 20,000 lb on each of the other four axres)
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From page 213... ...
Tnucx WercHr Lrurrs: lssurs ,q¡.,ro OprroNs gross weights over 80,000Ib, maximum axle weights would be limited as follows: . Single axles, L5,000 lb; .
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From page 214... ...
lmpacß of Proposed Changes -- - F"^"1" B - New formula ¿¿-¿-¿2-tttsEcoND AXLE TO LAST AXLE (ft) FIGIJRE 8-6 Maximum weight for five-axle double under New Approach formula and Formula B
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From page 215... ...
th o.:- 110 F -LoU 1oo3 Ø U> ocr90 o 208 Tnucx WrrcHr Lurs: lssurs ¡uo OpÏoNs ' 't20 '-t -- -t, -- -- -t -- -- - New formula I SS 60 65 70 75 80 sEcoND AXLE TO LAST AXLE (ft) FIGIJRE 8-8 Maximum weight for seven-axle Rocky Mountain double under New Approach formula and Formula B
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From page 216... ...
Impacß of Proposed Changes 140 -- - F"rm"l" B New ¡otmula I 8- 1303 I rzo o Ë 110 U)
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From page 217... ...
210 TRUCK WEtcHT L¡tr¡rs: lssurs ¡No OprloNs W: L,000(L12+62)
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From page 218... ...
lmpacß of Proposed Changes 211 Benefits of tractors with setback steering axles include better aerodynamics (which in turn provides better fuel economy and reduced splash and spray) , improved maneuverability due to a shorter wheelbase and sharper steering angles, more load-carrying capacity, easier cab entrance and exit for cab-over-engine configurations, and improved frontal energy absorption in collisions, because there is more space between the front bumper and the steering axles.
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From page 219... ...
212 Tnucx WrcHr Lr'lrs: lssues ¡No Oprlo¡ts TABLE 8-24 COST IMPACTS OF ALTERNATIVE SCENARIOS Change in Cost ($ billionsþar) Scenario Tlansport Pavement Bridges Total Grandfather Clause Elimination Uncapped Formula B NTWAC Proposal Canadian Interprovincial Limits TTI HS-20 Bridge Formula Uncapped TTI HS-20 Bridge Formula Combined TTI HS-20iFormula B +7.8 -2.t -5.4 -t1..7 -2.7 - 5.1 -5.2 -0.2 +0.0 +0.4 + 0.5 - 0.0 + 0.1 -0.0 - 0.3 +0.7 +3.0 +2.4 +0.3 + 0.4 +0.9 +7.3 -t.4 -2.0 - 8.8 -2.4 -4.6 -4.3 clause exemptions, most notably the higher axle weight limits in many eastern states.
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From page 220... ...
lmpacts of Proposed Changes 213 TABLE 8-25 OTHER IMPACTS OF ALTERNATIVE SCENARIOS Change in Scenario Percent Percent Heavy- Rail No. of Fatal Truck VMT Ton-Miles Accidents/Year Grandfather Clause Elimination +3.2 +0.8 +350 Uncapped Formula B -2.2 -2.2 -60 NT\ryAC Proposal - 1.1 -0.9 -40 Canadian Interprovincial Limits -6.3 -6.6 -430 TTI HS-20 Bridge Formula - 0.5 0.0 - 40 Uncapped TTI HS-20 Bridge Formula -2.2 -2.5 -40 Combined TTI HS-20Æormula B -2.5 -2.5 -110 their length limits, the diversion from rail to truck could be more than twice these estimates.
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From page 221... ...
214 Tnucx WncHr Lr'rrs: lssurs ¡Np OproNs Development. Report FIIWTVRD-85-088.
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From page 222... ...
9Findings and Recommendations THE LEGISLATION CALLING FOR this study-section 15g of the surface Tlansportation and uniform Relocation Assistance Act of LggT_ asked that the following four issuesl be addressed: . Elimination of existing grandfather provisions in federal weight regulations for Interstate highways; .
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From page 223... ...
216 Tnucr Wercnr Lrurs: lssu¡s nHo OploNs limits and added the federal bridge formula) contained grandfather clauses that allowed states to permit heavier vehicles to operate on the Interstate highway system without having to comply with federal gross and axle weight limits and the bridge formula, provided such vehicles were operating lawfully at the time the federal weight limits were enacted.
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From page 224... ...
F i ndi ngs and Recomme nd ation s 217 economies of states, the grandfather test itself is an arbitrary and inequitable means for determining such exemptions. Under the grandfather test, a state's request for an exemption is based on interpretations of its laws in L956 and L974, not on the likely consequences of granting the exemption.
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From page 225... ...
218 Tnucx Wncnr Lrurrs: lssu¡s nuo Oprto¡ts rates on another 63 billion ton-mi of truck-competitive traffic in order to avoid losing this traffic. These rate reductions will save shippers about $210 million, thus producing an estimated overall decline in gross rail revenues of $960 million annually, about 3.2 percent of base-case rail revenues.
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From page 226... ...
Findi ngs and Recomme ndations 219 that additional bridges be posted or replaced. Further, the shift offreight from rail to truck would also be greater if states responded by increasing length limits.
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From page 227... ...
Tnucx Wncnr Lwrrrs: lssurs nNo Opro¡¡s supported by an analysis of the added bridge costs associated with adopting a less restrictive criterion. When applied to the Interstate system, the current federal bridge formula is an overly cautious limit on weights for shorter trucks.
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From page 228... ...
Fi ndi ngs and Recommend ation s 221 TTI Bridge Formula In 1985 TTI completed a bridge formula development study for the Federal Highway Administration (FHWA)
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From page 229... ...
222 Tnucr WscHr Lrurrs: lssu¡s nNo Opro¡ts Combined TTI Hs-20/Formula B Applying the TTI HS-20 formula to axle groups with two to six axles and Formula B to axle groups with seven to nine axles is a third alternative. Thus, LCVs in western states could continue to operate over 80,000Ib at weights permitted by the current bridge formula, and shorter combinations and single-unit trucks could operate at weights permitted by the TTI HS-20 formula.
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From page 230... ...
Findi ngs and Recommendations 223 trailers and double-trailer combinations operating on designated highways in each of their jurisdictions. An important feature of the Canadian agreement is the absence of an explicit bridge formula.
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From page 231... ...
224 Tnucr WercHr Lrurs: lssurs ¡No OproNs tions to reach 80,000 lb ; however, certain operators-notably automobile haulers -- currently operate with front axle loads of 14,000Ib and adding a L2,000-lb steering-axle limit would hurt these operators. Summary Assessment of Bridge Formula Alternatives Of the various bridge formula alternatives evaluated by the committee, four were found to have merit as a potential basis for developing new truck weight regulatory policies: .
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From page 232... ...
F i ndi ngs and Recomme ndations 225 SPECIALIZED HAULING VEHICLES Specialized hauling vehicles are trucks with short wheelbases and specialized equipment for handling heavy loads. Tlpical examples of SHVs include dump trucks, solid-waste compactor trucks, and ready-mix concrete trucks.
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From page 233... ...
226 Tnucr WrrcHr Lrvrrs: lssurs ¡No OprroNs be subjected. Special permits for heavier-than-normal vehicles would be issued only if such loads did not exceed the operating rating of the bridges over which the vehicle would travel For purposes of analysis, the following gross weight limits were assumed in analyzing the NTWAC proposal: (a)
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From page 234... ...
F i ndi ngs and Recomme nd ation s 227 appropriate for vehicles that have difficulty operating under the current formula. Nonetheless, the committee finds the maximum weights proposed by NTWAC to be overly permissive when applied with the relatively broad definition of SHV used for this study.
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From page 235... ...
228 Tnucr Wnc¡rr Lr¡¡rrs: lssues ¡No Oplons STUDY RECOMMENDATIONS The impact ânalyses conducted for this study support findings from previous congressionally mandated truck size anù weight studies that increasing truck weights can significantly reduce the cost of goods movement and that cost savings because of more efficient trucks generally exceed the additional pavement and bridge costs incu¡red by highway agencies. At the same time, other study findings suggest the need for caution in implementing increases in truck weights.
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From page 236... ...
F i nd i ngs and Recom me nd ati on s Following are five recommendations that the committee believes are consistent with these objectives.a Recommendation 1: New Bridge Formula Congress should replace the current federøl bridge formula on Interstate highways with the following formula: W= 1,000(2L+26)
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From page 237... ...
230 Tnucx W¡rcnr Lr¡¿rrs: lssu¡s AND OploNs mula on Interstates should serve to attract heavy-truck traffic from other roads. The shift of heavy trucks from non-Interstate to Interstate highways would reduce pavement costs to highway agencies, because on a pervehicle-mile basis, the pavement wear effects of heavy trucks are much less on thicker pavements.
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From page 238... ...
Fi ndings and Recommendations 23"1 The impact analyses conducted for this study indicate that inc¡eases in weight limits beyond the recommended formula would, more likely than not, result in additional savings; however, our ability to anticþate all the important consequences of such increases is limited. The committee's recommended bridge formula is the result of striking a balance between the objectives of maximizing net savings and minimizing uncertainty about the consequences of changes in limits.
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From page 239... ...
232 Tnucr W¡cHr Lrurs: lssues ¡¡¡o Oplo¡rs permit programs would contribute to improved highway safety. Specific topics to be considered in establishing special safety regulations for permit operatinns include the following: -Power requirements for acceleration and hill climbing; -Driv er qualifications ; -Accident reporting and insurance requiremenß; -Braking systems; -Connecting equipment such as fifth wheels, pick-up plates, kingpins, and hitch connections; and -Axle width, tires, and rims.
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From page 240... ...
Fi ndi ngs and Recommendations 233 undesirable at weights over 80,000Ib, because they cause relatively high pavement wear per unit of freight hauled. Under a permit program, these vehicles could be banned or charged higher permit fees commensurate with the damage they add to pavements.
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From page 241... ...
234 Tnucr Wgcnr LtMtrs: lssuEs RNo Oplo¡.ls ' Initially restrict permit vehicles to routes without deficient bridges and then apply permit revenues as they become available to expand the routes open to permit vehicles. ' Restrict weights for permit vehicles based on an analysis of the loadbearing capacity of individual bridges.
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From page 242... ...
Findings and Recommendations Also, several states exempt certain types of vehicles from the bridge formula. For example, Michigan allows vehicles over 80,000Ib that exceed Formula B by a considerable amount, and Arkansas and Pennsylvania apply Formula B only to vehicles over 73,280Ib.
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From page 243... ...
236 Tnucr WrrcHr LtMtrs: lssuEs ¡No Oplorus highways, which are more su.sceptible to damøge by ilregally overweight tr_uc$. lhese efforß should include more weight enþr""*
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From page 244... ...
F i ndi ngs and Recommendations 237 REFERENCES ABBREVIATIONS AASHTO American, Association of State Highway and Transpoitatiou OfficialsDûT U.S. Department of TlansportationTRB Tbansportation Research Board AASIITC,.
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From page 245... ...
APPENDIX A Section 1 5B of the Surface Transportation and Uniform Relocation Assistance Act of 1987 SEC.
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From page 246... ...
Tnucx WrrcHr Llurs: lssurs ¡to OpÏoNs 80,000-pound gross vehicle weight limit maximums authorized by the Fede¡al-Aid Highway Amendments of 1974 (Public Law 93-643) ,including permits for divisible loads and statutory provisions providing higher weights by formula, tolerance or statutory specification.
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From page 247... ...
APPENDIX B Pavement lmpact Analysis Methodology The data, methods, and assumptions used to produce estimates of the effects of alternative truck weight regulatory scenarios on costs for new and reconstructed pavements and for resurfacing and other forms of pavement rehabilitation are described here. The cost estimates were developed under the assumption that if traffic loadings on pavements were increased, highway agencies would be able to increase pavement expenditures so that the condition of the system was maintained at the same level that would have occurred without the increase in loadings.
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From page 248... ...
1A') Tnucr W¡lcHr Llutts: lssues nNo Oplor.ls ment expenditures by highway agencies were also increased (or de,crcased)
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From page 249... ...
Appendix B: Pavement Impact Analysis Methodology 243 most common method remains the application of substantial asphalt concrete overlays to foundation pavement surfaces of either flexible (asphalt concrete) or rigid (portland cement concrete)
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From page 250... ...
leveling courses, milling, joint repair, subdrainage improvements, and traffic control. clearly each added ESAL affects overlãy thickness and, accordingly, the variable-cost component of an overlay.
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From page 251... ...
TABLE B-1 ADDED PAVEMENT REHABILITATION COST FOR 10 PERCENT MORE ESALS Added Cost ($ millions per year) Pavement T!
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From page 252... ...
246 Tnucx Welcnr Llvrs: lssu¡s AND OploNS where xis the added cost for a 10 percent increase in traffic loadings and Y is the increase (or decrease) in traffic loadings for the scenariã, expressed as a percent of base-case traffic loadings.
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From page 253... ...
TABILE B-2 PAVEMENT COSTS FOR NEW AND RECONSTRUCTED HIGHWAYS Pavement Tþe and Highway Classification Tþical Structural Numbef Average Width (fÐ Pavement Cost ($/mile) Flexilile pavements Rural Interstate O$er rural Urban Interstate Otþr urban Rigid;,;pavements Rural Interstate Other rural Urban Interstate Other urban 5 J 5 3 72 10 72 10 75.3 n.1 91.4 34.9 78.9 39.1 94.8 49.4 738,000å 159,000à 896,000ó 205,000ö 912,000 377,00V l-,096,000' 476,000' " Structural number is converted to inches of asphalt concrete by dividing by 0.44.å Assuining a unit cost of $52.V21yd3 for asphalt concrete.
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From page 254... ...
248 Tnucr Wrrcnr LtMtTs: lssuEs nNo Oplous where M is the annual mileage of new and reconstructed pavement for the region and highway system and C is pavement-related cost per mile constructed. The 0.015 factor in the above equation is derived from AASIITO's pavement design equations.
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From page 255... ...
TABT E B-3 NEw AND RECONSTRUCTED PAVEMENTS: ADDED coST FOR 10 PERcENT MORE ESALS Added Cost ($ millions/year) Paverrient Type and Reei Flexibfe pavement New England Mid'Atlantic South Atlantic Midwest Soufh Central Western LCV Othþr Westem Totål Rigid pavement New England Mid.Atlantic Soulh Atlantic Midwest Soulh Central 'Western LCV OthBr Western Rural Interstate Other Rural Urban Interstate Other Urban Total Tot4l 0.13 0.1.9 0.29 0.29 0.23 0.67 0.65 2.45 0.01 0.23 0.33 0.53 0.18 0.28 0.40 r.96 0.42 L.45 1.94 2.58 7.47 1.49 2.51, 11.86 0.01 0.21 0.07 0.88 0.08 0.08 0.1.9 L.52 0.1L 0.11" 0.1.L 0.19 0.06 0.06 0.16 0.80 0.0L 0.2t 0.14 0.22 0.09 0.09 0.29 1.05 0.a 0.97 0.82 1.03 0.38 0.32 L.23 s.17 0.03 0.30 0.06 0.51 0.11 0.06 0.33 1.40 1.08 2.72 3.16 4.09 2.L4 2.54 4.55 20.28 0.07 0.94 0.59 2.t6 0.46 0.51 7.20 5.93
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From page 256... ...
TABLE B-4 SUMMARY OF PAVEMENT IMPACT ANALYSIS Percent Change in ESAL-Mles Change in Pavement Costs($ miltions per year) Scenario Flexible RiCrd Flexible RiCrd Total Grandfather Clause Elimination Uncapped Formula B NTWAC hoposal Canadian Interprovincial Limits TTI HS-20 Bridge Formula Uncapped TTI HS-20 Bridge Fìormula Combined TTI Hs-20/Bridge Formula B -6.0 +I.2 +8.5 +15.2 -0.9 +5.5 +0.4 -5.7 -4.8 +8.5 +8.4 -0.5 -0.1 - 3.5 -187.4 +34.4 +299.3 +435.7 -40.4 + 136.8 +8.1 -27.4 -26.5 +52.2 +55.6 -2.7 +2.9 -17.5 -274.8 +7.9 +351.5 +49t.3 -43.L +139.7 -9.4
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From page 257... ...
Appendix B: Pavement lmpact Analysis Methodology 251 PAVEMENT IMPACT ANALYSIS RESULTS Table B-4 is a summary of pavement impact analysis results for the seven truck weight scenarios that were examined by this study. The table shows percent changes in ESAL-miles for flexible and rigid pavements.
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From page 258... ...
APPENDIX C Sensitivity Analysis for Safety lmpacts The results of a sensitivity analysis to examine how estimates of the safety impacts of alternative scenarios would be affected by different assumptions about the relationship between gross vehicle weight (G\lfV) and accident rates are presented in this appendix.
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From page 259... ...
Appendix C: Sensitivity Analysis for Safety lmpacß 253 where R and R' are base and adjusted accident rates, G and G' are average GWVs for the base case and alternative scenarios, and È is a constant term. The constant k reflects the extent to which changes in average GVIV are expected to affect accident rates.
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From page 260... ...
APPENDIX D Pavement Effects of lllegally Overweight Trucks Pavement cost savings are analyzed that would result if all illegally overweight trucks were forced to operate at legal limits for axle weights. For simplicity, the analysis focuses on tandem axles, which account for over 70 percent of the equivalent single-axle load (ESAL)
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From page 261... ...
Appendix D: Pavement Effecu of lllegally OverweightTrucks 255 TABLE D.1 HYPCIHETICAL TANDEM-AXLE WEIGHT DISTRIBUTIONS FOR ANALYSIS OF PAVEMENT IMPACTS OF ELIMINATING ILLEGALLY OVERWEIGHT TRUCKS TandemAxle Weight (kipÐ 1.0 Percent Overweight 20 Percent Overweight Percentage Distribution of Tandem Axles 6I 10 L2 L4 T6 18 20 22 u 26 28 30 32 34 36 38 40 42 44 46 48 50 4.1 4.1 5.3 6.3 4.3 4.0 4.0 3.7 3.9 3.8 3.9 4.7 8.0 13.2 1,6.7 8.0 r.6 0.3 0.1 0.0 0.0 0.0 0.0 3.6 3.6 4.7 5.6 3.9 3.6 3.6 3.3 3,5 3.4 3.4 4.t 7.t 11..7 14.8 7.6 4.8 3.0 1..9 1..2 0.8 0.5 0.3 proportional to changes in ESAL-miles, it was estimated that the effect of eliminating illegally overweight axle loads would be to reduce pavement costs by $160 million to $670 million per year.
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From page 262... ...
APPENDIX E lndividual Statements of Committee Members Louis C Nappi and Stephen H
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From page 263... ...
Appendix E: lndividual Staternents of Committee Members 257 federal weight limits when empty, in order to carry out the jobs for which they are designed. They cannot meet federal standards, particularly the bridge formula, without sacrificing productivity and/or safety.
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From page 264... ...
258 TRucr W¡rcnr LtMtrs: lssuEs ¡No OpÏoNs wheelbase vehicles used for heavy hauling in such industries as con_ struction and solid waste collection; this is transportation activity ïn which configuration of longer vehicles with additional axles does not ap,pe.ar feasible in view of the need for vehicles to maneuver through relatively narrow streets. Despite its Congressional charge, the Report of the Tiuck Weight Study Committee really does not ',focus" on the problems of SHVs.
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From page 265... ...
Appendix E: lndividual Statements of Committee Members 259 operation without regard to federal gross or axle weight limits or the bridge formula. This was initially proposed by the National Tiuck Weight Advisory Council (NTWAC)
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From page 266... ...
Tnucx WucHr Llurrs: lssurs AND OploNs Bridges ! 1der the proposed permit program, SHVs would be exempt from thefederal bridge formula.
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From page 267... ...
6Àg I 4000 Ég zË roooo o I aooo t¡¡ Appendix E: lndividual Statements of Committee Members 261 SPAN (FEETI AASHTO HS15-44 LOADING (ADJUSTED FOR IMPACTI Attachment A annually, probably to HS25 or greater, but this too is not factored into the cost estimates for deficient bridges.
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From page 268... ...
ô o. Y I a000 t-lr Þ2 E 3oooo .
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From page 269... ...
6À Y I t000 Élt F2E sooooã o( I 2ooo t¡¡ Appendix E: lndividual Statements of Committee Members 263 ta0 SPAN (FEETI AASHTO HS2O-I4 LOADING (ADJUSTED FOR IMPACT) Attachment A (continued)
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From page 270... ...
Tnucx Wercnr LtMtrs: lssuEs ¡No Opno¡rs oÀ Y I É,lt t-t¡¡ .o =ô o ul 5 I / / / ', / è, / / / ^a' ,ttt' / .a { -a :9:' ) 7 ,tjy ./ / l: é Ø tooo SPAN (FEET} AASHTO HS2O-44 LOADING (ADJUSTED FOR IMPACTI Attachment A, (continued)
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From page 271... ...
3000 2000 o o. Y I Élt t-z u¡ o =ô oJ u¡ J Appendix E: lndividual Staternents of Committee Members 265 SPAN (FEETI PROPOSED HS25-44 LOADING (ADJUSTED FOR IMPACT)
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From page 272... ...
TRucr WercHr Lru¡rs: lssurs ¡uo OprroNs õ 'û Yl,- aooo Ég ÞzE 3oooo o I 2ooo u¡ SPAN (FEET' PROPOSED HS25-44 LOADING (ADJUSTED FOR IMPACT) Attachment A (continued)
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From page 273... ...
Appendix E: lndividual Statements of Committee Members 267 to00 oÀ Y I l-¡l. t'.z u¡ o =o o u¡ J 180 SPAN (FEETI PROPOSED HS3O-44 LOADING (ADJUSTED FOR IMPACT} Attachment L (continued)
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From page 274... ...
ut o. v I Élt -t¡¡ =o =o oJ lrl Tnucx WrrcHr Lr¡rrs: lssues nuo Opr¡o¡ts to00 looo SPAN (FEET} (ADJUSTED FOR IMPACT} Attachment A (continued)
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From page 275... ...
Appendix E: Individual Statements of Committee Members 269 6G v I Flr Fz u¡ =o =o o ul 5000 2000 1000 t0c0a0 TRUCK "4" LIVE LOAD MOMENT SPAN (FEETI DIAGRAM Attachment lr (continued) tion led the Advisory Committee to conclude that the annual cost of bridge fatigue and pavement damage attributable to permit vehicles is small.
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From page 276... ...
270 Tnucx W¡rcHr Lrvlrs: lssurs Rno OploNs õ o. vI rooo Élt zE soooo =o oJ 2ooo tll J 6000 20 a0 TRUCK -D" SPAN (FEETI LIVE LOAD MOMENT DIAGRAM Attachment A (continued)
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From page 277... ...
Appendix E: Individual Statementi of Committee Members 27"1 Attachment B (TRB Special Report 618: The AASHO Road Test-Pavement Research, 1962)
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From page 278... ...
272 Tnucx WrrcHr Ltu¡rs: lssues ¡No OprtoNs limitations that might be set, routing and posting restrictions, the permit fees and penalties, all would be left up to the state should it decide to adopt a permit program. Congress would protect its investment in the federal aid system by establishing minimum requirements and assuring that these standards were complied with by the state.
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From page 279... ...
Appendix E: lndividual Statements of Committee Members 273 It is my hope that the Congress will take the Committee's findings and authorize any state to be able to adopt a permit program for specialized hauling vehicles, regardless .of grandfather clause status, so long as it meets minimum federal standards to assure protection of pavements and bridges and enforcement. The permit program proposed by the National Truck Weight Advisory Council meets this criteria and should serve as the foundation for Congress' effort.
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From page 280... ...
274 Tnucr WrrcHr Lrurrs: lssu¡s ¡No OploNs from adoption of each of the positions identified and analyzed. Related issues of permitting, weight enforcement, and data availability and reliability shall be addressed as appropriate.
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From page 281... ...
Appendix E: Individual Statements of Committee Members 275 over time. Overlaying sampling data on the volume of truck traffic and types of vehicles can then provide some form of basic data from which to extrapolate into the scenarios of Chapter 8 to determine potential enforcement impacts.
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From page 282... ...
276 TRUCK WEICHT LIMITS: IssUEs AND OPTONS The Final Report also notes that both Recommendation 1, New Bridge Formula, and Recommendation 2, Special Permit Programs, will increase the number of bridges that will require load posting. As with any permit system, compliance by the industry with restrictions on routings, including load-posted bridge restrictions, is voluntary.
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From page 283... ...
Appendix E: lndividual Statements of Committee Members 277 compliance with the law, reality dictates that the absence of effective enforcement seriously erodes the assumption (GAO 1979; DOT 1983)
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From page 284... ...
278 Tnucx Wercur Lrurs: lssurs n¡lo Opr¡o¡rs of legally loaded trucks, the shortening of [pavement] life would be about 6.2 percent." The conclusion then noted that (Barros 1985, 9)
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From page 285... ...
Appendix E: Individual Statements of Committee Members 279 Fines and Penalties . Develop a mandatory fine structure for violation of weight limits that reflects the fourth-power damage coefficient to pavement.
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From page 286... ...
280 Tnucx W¡tcnr LMrls: lssuEs ¡No Optrorls as a safety violation under existing or amended Federal Motor carrier safety and/or Tfansportation of Hazardous Materials Regulations, thereby requiring the vehicle be placed out of service until it is brought into compliance. ' Establishment of a liaison through FHWA to act as a coordinator for coopêtative enforcement efforts with contiguous states.
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From page 287... ...
Appendix E: lndividual Statements oÍ Committee Members 281 REFERENCES ABBREVIATIONS DOT GAO U.S. Department of Tlansportation General Accounting Office MnDOT-DPS Minnesota Department of Tlansportation and Department of Public Safety Barros, R.T.
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From page 288... ...
APPENDIX F Truck Cost lmpacts by Region In the productivity analysis conducted for this study, the United States was divided into seven regions, as shown in Figure 3-1. The regions were defined primarily on the basis of similarity of size and weight limits and geographical contiguity.
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From page 289... ...
Appendix F: Truck Cost lmpacts by Region 283 network. Michigan, on the other hand, has the nation's highest GVW limits (149,000Ib for vehicles with 1L axles)
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From page 290... ...
TABLE F-1 EFFECTS OF UNCAPPED FORMULA B SCENARIO ON TRUCK COSTS BY REGION Change in Costs' ($ millions 1988 per year) For Combinations For All Trucks As Percent of Base-Case Costs Regron New England (Conn., Maine, Mass., N.H., R.I., Vt.)
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From page 291... ...
Appendix F: Truck Cost lmpacts by Region 285 New England regions (0.3, 0.6, and 0.9 percent, respectively)
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From page 292... ...
TABLE F-2 EFFECTS OF NTWAC PROPOSAL ON TRUCK COSTS BY REGION Change in Tiransport Costs' Single-Unit Trucks Combination Tiucks Total Dollarså Percent Dollarsä PercentRegion Dollarsä New England (Conn., Maine, Mass., N.H., R.I., Vt.) Middle Atlantic(D.C.; Del., Md., N.J., N.Y., Pa.)
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From page 293... ...
South Centfal -178 -2.2 -wZ -0.7 -æ0 -1.2(Ala., Ark., Ky., La., Miss.o Tþnn.) \üestern LClf -UZ -3.7 -48 -0.5 -290 -t.9(Alaska, Idaho, Mont., N.Dak., Nev., Orèg., S.Dak., Utah, lVash., Wyo.)
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From page 294... ...
TABLE F.3 EFFECTS OF CANADIAN INTERPROVINCIAL LIMITS SCENARIO ON TRUCK COSTS BY REGION Change in Tiansport Costs" Single-Unit Combination Trucks Tiucks Total Regron D"lL"*
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From page 295... ...
South Central(Ala., Ark., Ky., La., Miss., Tenn.) Western LCV' (Alaska, Idaho, Mont., N.Dak., Nev., Oreg., S.Dak., Utah, Wash., Wyo.)
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From page 296... ...
RIO ON TRUCK COSTS BY REGION Change in Transport Costs" Single-Unit Tiucks Combination Tiucks Total Region Dollarsá Percent Dollarsó Percent Dsllarså PercentNew England (Conn., Maine, Mass., N.H., R.I., Vt.) Middle Atlantic (D..C., Del., Md., N.J., N.y., Pa.)
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From page 297... ...
-L4 -O.2 -283 - 1.9 -297 - 1.3 -na -4.L -181 -2.4 -451 -2.9 -L,442 -5.7 -73i -2.L -2,L75 -3-6 -2J33 -3.0 -2,? Á6 -1.9 -4,999 -2.4 " Excludes effects of modal diversion.å In mittiorns of 1988 dollars per year.
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From page 298... ...
TABLE F-5 EFFECTS OF COMBINED TTI HS-2O/FORMULA B SCENARIO ON TRUCK COSTS BY REGION Change in Transport Costs" Region Single-Unit Trucks Combination Trucks Dollarså PercentDollarså Percent Dollarsá Percent New England (Conn., Maine, Mass., N.H., R.I., Vt.) Middle Atlantic (D.C., Del., Md., N.J., N.Y., Pa.)
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From page 299... ...
South Central (Ala., Ark., Ky., La., Miss., Tenn.) Western LC\f (Alaska, Idaho, Mont., N.Dak., Nev., Oreg., S.Dak., Utah, Wash., Wyo.)
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From page 300... ...
APPENDIX C Productivity lmpact Analysis Methodology This appendix provides a description of the methods used to estimate theproductivity impacts of alternative truck weight scenarios. The principal topics include the following: ' Tluck costs: costs per vehicle mile and per payload ton-mile were developed from a detailed study of all sourcesãndlróm the motor carrier interviews as a primary basis for forecasting how carriers and shþers are expected to respond tothe scenarios by shifting to different truck ðonfigurations or by shifting between rail and trucÈ modes of transportatiãn.
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From page 301... ...
Appendix C: Productivity lmpact Analysis Methodology 295 cost per ton, and cost pqr ton-mile. For the purpose of the analyses performed in this study, cost per ton-mile is the most useful of these measures, though, like the others, it has its limitations.
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From page 302... ...
296 Tnucx Wrcnr Lrurs: lssurs ¡ruo OprroNs Cost per Vehicle Mile Cost per vehicle mile was estimated by obtaining separate estimates of six components of cost as a function of configuration and GVTV. The six cost components, and influences on their values that are reflected in the cost functions used, are .
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From page 303... ...
TABLE G-1 SELECTED COST ESTIMATES FOR TRUCKLOAD OPERATION OF VANS (Faucett Associates L990) Configuration Loaded Weight (lb)
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From page 304... ...
Tnucx WncHr Ltvlrs: lssues RNo Opllor.ls empty mileage ratios that are higher or lowe¡ than those used in these estimates, costs per loaded mile and per payload ton-mile will be higher or lower than those shown. However, the comparisons shown in Table G-l are expected to be valid in such cases because the costs would tend to go up or down uniformly; for any pair of comparable configurations, tñe relationships of the costs per loaded mile and costs per ton-mile would not change significantly.
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From page 305... ...
Appendix C: Productivity lmpact Analysis Methodology savings than five-axle twins when the two configurations are loaded to bridge formula limits, but that the heavier configuration is appreciably less attractive for carrying cube-limited cargo. It is at a substantial disadvantage for carrying weight-limited cargo under an 80,000-lb limit.
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From page 306... ...
300 Tnucx WncHr Lrvlrs: lssurs AND OpToNs transported by vehicle configuration and region and (b) the effects on transport costs by region.
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From page 307... ...
Appendix C: Productivity lmpact Analysis Methodology 301 6. For each relevant combination of current and new vehicle type, develop functions representing average cost of transport in the current and new configurations as functions of ton-miles and VMT.
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From page 308... ...
302 TRucr W¡lcHr Lrurrs: lssurs ¡No Oplo¡rs base-case payload ton-miles carried by five-axle twins and six-axle twins were redistributed across weight ranges using the distributions obtained for five-axle twins and six-axle twins, respectively. MODAL DIVERSION Any change in the cost of using trucks for rnedium- and long-distance hauls has the potential for resulting in some diversion of traffic between rail and truck.
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From page 309... ...
Appendix C: Productivity lmpact Analysis Methodology . A decrease in transport costs results in a reduction in the price of goods, which, in turn, may produce increased demand for either these goods or for some other goods.
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From page 310... ...
Study Committee Biograph ical lnformation Lestei A Hoel, Chairman, is }lamilton Professor of Civil Engineering, University of Virginia, and was Chairman of the Department from 1974 tD 1989.
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From page 311... ...
Study Comm¡ttee Bìographìcal lnformation 305 State University, San Jose, in 7952 andhis M.S. in civil engineering from Auburn University in 1958.
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From page 312... ...
306 Tnucr WrrcHr Llulrs: lssu¡s AND OploNs stephen H Monson is a Deputy Attorney General for the State of New Jersey.
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From page 313... ...
Stu dy Co m m ittee B i og,r aph ical I nfor m atì on 307 of Maryland in 1983. He is a Fellow of the Institute of Tiansportation Engineering, serving as Chairman of the Committee on Student Chapters and as Vice hesident of the North Carolina Section.
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