Review of Truck Characteristics as Factors in Roadway Design (2003)

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5CHAPTER 2 TRUCK SIZE AND WEIGHT LIMITS This chapter addresses the current size and weight limits for trucks as imposed by federal and state governments. These limits set the framework under which trucks currently on the road operate. Changes in these limits are a primary mecha- nism by which future changes in truck characteristics that affect highway geometric design might occur. FEDERAL TRUCK SIZE AND WEIGHT LIMITS Current federal law includes the following limits on truck size and weight: • States may not set maximum weight limits on the Inter- state System less than – 36,400 kg [80,000 lb] gross vehicle weight: – 9,100 kg [20,000 lb] for a single axle: or – 15,500 kg [34,000 lb] for a tandem axle. • States must permit weights for other axle groups so long as the weight on the axle group does not violate the fed- eral bridge formula and the gross vehicle weight does not exceed 36,400 kg [80,000 lb]. • States must permit tractor-trailer combination trucks with trailer lengths up to 14.6 m [48 ft] in length to oper- ate on the National Network (NN). • States must permit combination trucks consisting of two trailers with lengths up to 8.7 m [28.5 ft] per trailer to operate on the NN. • States must permit trucks within the length limits given above with widths up to 2.6 m [8.5 ft] to operate on the NN. The NN is a network of routes designated by the Secretary of Transportation in consultation with the states. The NN consists of the Interstate System and other selected routes. The extent of the NN on non-Interstate routes varies by region of the country. Typically, the non-Interstate routes in the NN are fairly limited in the eastern states and more exten- sive in the western states. In this report, the phrase tandem axle, without modifiers, refers to a pair of axles separated from one another by 1.2 m [4 ft], nominally. A common practice is to spread these axles further apart (called spread tandems) to allow a greater legal weight limit. For example, if they are separated by 3 m [10 ft], their maximum weight limit is 18,200 kg [40,000 lb], twice the limit for a single axle. The federal bridge formula referred to above is W = 500[LN/(N-1) + 12N + 36], where W is the maximum weight in pounds carried on any group of two or more axles, L is the distance in feet between the extremes of any group of two or more axles, and N is the number of axles under consideration. STATE TRUCK SIZE AND WEIGHT LIMITS States set the truck size and weight limits on their facili- ties within the framework set by the federal limits discussed above. Many states have established truck size and weight limits that exceed those mandated by the federal government. For example, many states permit tractor-semitrailers with 16.2-m [53-ft] trailers to operate on the NN, even though fed- eral law requires only that 14.6-m [48-ft] trailers be permit- ted. Many states also permit trucks with gross weights over 36,400 kg [80,000 lb] and trucks with trailers longer than those mandated by federal law to operate under permit on specified highways and/or under specified conditions. The federal truck size and weight limits discussed above were established by the Surface Transportation Assistance Act (STAA) of 1982. The 1991 Intermodal Surface Transportation Efficiency Act (ISTEA) instituted a freeze on increases in state size and weight limits for Longer Combination Vehicles (LCV). State limits in effect were allowed to remain in place (“grandfathered”), but no further increases in those limits have been permitted. ISTEA defined an LCV as . . . any combination of a truck tractor with two or more trail- ers or semitrailers which operates on the Interstate System at a gross vehicle weight greater than 80,000 lb. Current state limits on truck sizes and weights for Inter- state and non-Interstate highways are discussed below. Table 1 summarizes general truck weight limits for each of the 50 states and the District of Columbia based on informa- tion from the FHWA Comprehensive Truck Size and Weight (CTSW) study (5). The table includes limits for gross vehi- cle weight, single-axle weight, and tandem-axle weight for Interstate highways and other highways. The table also indi- cates whether the state uses the federal bridge formula and the weight limits for which the state issues “routine” permits.

There are no overall maximum vehicle length limits on the NN, including the Interstate System. Instead, there are maxi- mum limits on trailer lengths. This approach is intended to discourage trucking companies from decreasing tractor length to increase box length. On highways other than the NN, states are free to impose maximum overall vehicle length limits. As noted above, states must permit 14.6-m [48-ft] trailers on single-semitrailer combination trucks and 8.7-m [28.5-ft] trail- 6 ers on double-trailer combination trucks on the NN. States can permit single semitrailers that are longer than the federal minimums on the NN and on other highways. Some states allow longer semitrailers but impose a maximum kingpin-to- center-of-rear-axle (KCRA) or kingpin-to-center-of-rear- tandem (KCRT) distance to limit truck offtracking. A 14.6-m [48-ft] semitrailer and a 16.2-m [53-ft] semitrailer with the same KCRA or KCRT distance will offtrack by the same TABLE 1 General state weight limits (in units of 1,000 lb) (5) Gross vehicle Single axle Tandem axle Federal bridge formula “Routine” permit State Interstate Other hwys Interstate Other hwys Interstate Other hwys Interstate Other hwys Gross vehicle weight(a) Single axle Tandem axle Alabama 80 84 20 20 34 40 Yes No-WT 110/150 22 44 Alaska – 90(b) – 20 – 38 – Yes 88.6(b)/150 30 50 Arizona 80 80 20 20 34 34 Yes No-WT 106.5(c)/250 28 46 Arkansas 80 80 20 20 34 34 Yes Yes 102/134 20 40 California 80 80 20 20 34 34 Yes-mod Yes-mod 119.8(d) (e) 30 60 Colorado 80 85 20 20 36 40 Yes No 127/164 27 50 Connecticut 80 80 22.4 22.4 36 36 Yes Yes 120/160 22.4 NS Delaware 80 80 20 20 34 40 Yes No-WT 120/120 20 40 D. C. 80 80 22 22 38 38 Yes-mod Yes-mod 155-248 31 62 Florida 80 80 22 22 44 44 Yes(f) No-WT 112/172 27.5 55 Georgia 80 80 20.34 20.34 34(g) 37.34 Yes Yes(f) 100/175 23 46 Hawaii 80.8 88 22.5 22.5 34 34 Yes No Case-by-case above normal limits Idaho 80 105.5 20 20 34 34 Yes Yes Case-by-case above normal limits Illinois 80 80(h) 20 20(i) 34 34(i) Yes Yes(i) 100/120 20 48 Indiana(j) 80 80 20 20 34 34 Yes Yes 108/120 28 48 Iowa 80 80 20 20 34 34 Yes Yes 100/160 20 40 Kansas 80 85.5 20 20 34 34 Yes Yes 95/120 22 45 Kentucky 80 80(k) 20 20 34 34 Yes Yes 96/140 24 48 Louisiana 80(l) 80(l) 20 22 34 37 Yes No 108/120 24 48 Maine 80 80(m) 20(n) 22.4 34 38 Yes-mod No 130/167 25 50 Maryland 80 80 20(o) 20(o) 34(o) 34(o) Yes Yes 110/110 30 60 Massachusetts 80 80 22.4 22.4 36 36 Yes Yes 99/130 NS NS Michigan(p) 80 80 20 20 34 34 Yes Yes 80/164 13 26 Minnesota 80 80(q) 20 18 34 34 Yes Yes-mod 92/144 20 40 Mississippi 80 80 20 20 34 34 Yes Yes 113/190 24 48 Missouri 80 80(r) 20 20(r) 34 34(r) Yes Yes(r) 92/120 20 40 Montana 80 80 20 20 34 34 Yes Yes 105.5/126 20 48 Nebraska 80 95 20 20 34 34 Yes Yes 99/110 20 40 Nevada 80 129(s) 20 20 34 34 Yes Yes 110(t)(u) 28 50.4 New Hampshire 80 80 20(o) 22.4 34(o) 36 Yes No 130/150 25 50 New Jersey 80 80 22.4 22.4 34 34 Yes No 100 /150(v)(v) 25(v) 40(v) New Mexico 86.4 86.4 21.6 21.6 34.32 34.32 Yes-mod Yes-mod 104(w)/120 26 46 New York 80 80 20(x) 22.4 34(x) 36 Yes(x) Yes(x) 100/150 25 42.5 North Carolina 80 80 20 20 38 38 Yes-mod Yes-mod 94.5/122 25 50 North Dakota 80 105.5 20 20 34 34 Yes Yes 103/136 20 45 Ohio 80 80 20 20 34 34 Yes No 120/120 29 46 Oklahoma 80 90 20 20 34 34 Yes Yes 95/140 20 40 Oregon 80 80 20 20 34 34 Yes-mod Yes-mod 90/105.5 21.5 43 Pennsylvania 80 80 20(y) 20(y) 34(y) 34(y) Yes(y) Yes(y) 116/136 27 52 Rhode Island 80 80 22.4 22.4 36 36 Yes-mod Yes-mod 104.8(u) 22.4 44.8 South Carolina 80 80 20 22 34(z) 39.6 Yes(z) No 90/120 20 40 South Dakota 80 129(s) 20 20 34 34 Yes Yes 116(u)(aa) 31 52 Tennessee 80 80 20 20 34 34 Yes Yes 100/160 20 40 Texas 80 80 20 20 34 34 Yes-mod Yes-mod 106.1(bb)/120 25 48.125 Utah 80 80 20 20 34 34 Yes Yes 100/123.5 20 40 Vermont 80 80 20 22.4 34 36 Yes Yes 108(cc)/120 24 48 Virginia 80 80 20 20 34 34 Yes Yes 110/150 25 50 Washington 80 105.5 20 20 34 34 Yes Yes 103/156 22 43 West Virginia 80 80(dd) 20 20 34 34 Yes Yes 104/110 20 45 Wisconsin 80 80 20 20 34 34 Yes-mod Yes-mod 100/191 20 60 Wyoming 117 117 20 20 36 36 Yes No 85/135 25 55 NS Not specified. WT Weight table. Footnotes to this table are presented on the next page. Information sources: J. J. Keller & Associates, Vehicle Sizes and Weights Manual. July 1, 1994. Specialized Carriers & Rigging Association (SC&RA), Permit Manual. July 19, 1994. Western Association of State Highway and Transportation Officials (WASHTO), Guide for Uniform Laws and Regulations Governing Truck Size and Weight. June 26, 1993.

amount in making a given turn, so the rear tires of the 16.2-m [53-ft] semitrailer are no more likely to encroach on a shoul- der or curb than the rear tires of the 14.6-m [48-ft] semi- trailer. However, because of the greater distance from the rear axle to the rear of the trailer, the rear of the trailer will follow a path outside the rear axles of the truck. Table 2 summarizes the maximum semitrailer lengths per- mitted by states in 1994 on the NN and on other state high- ways. Both the maximum trailer length and any kingpin dis- tance restrictions are noted. In addition, any overall length restrictions for highways not in the NN are noted. 7 State size and weight limits for LCVs are frozen at early 1990s levels under the provisions of ISTEA. Table 3 shows the current weight limits for trucks over 36,400 kg [80,000 lb] with two or three trailers in states where LCVs are permitted to operate. The highest gross vehicle weight limits are 74,500 kg [164,000 lb] in Michigan; such heavy trucks must typically have 10 or more axles to meet Michigan requirements. In eastern states, LCVs are typically restricted to operate on specific turnpikes or toll roads. In some western states, LCVs operate more generally on both Interstate and non-Interstate highways. TABLE 1 (Continued) NOTES TO TABLE 1: (a) “Routine” Permit Gross Vehicle Weight: the first number (left) is the highest weight a five-axle unit can gross before special (other than routine) review and analysis of an individual movement is required. The second number (right) is the highest gross weight any unit with sufficient axles can gross before special review is required. (b) State rules allow the more restrictive of the federal bridge formula or the sum of axle weight limits. The five-axle “routine” permit value is estimated using a truck tractor-semitrailer with a 65-ft spacing between the front and rear axles (based on a 48-ft semitrailer). (c) The five-axle “routine” permit value is estimated using a truck tractor-semitrailer with two tandem axles at 47,250 lb each and a 12,000 lb steering axle. (d) Estimate based on State weight table values for a tandem drive axle at 46,200 lb, a rear tandem at the 60,000 lb maximum, and a 12,500 lb steering axle. (e) Maximum based on the number of axles in the combination. (f) Federal bridge formula applies if gross vehicle weight exceeds 73,280 lb. (g) If gross vehicle weight is less than 73,280 lb, the tandem axle maximum is 40,680 lb. (h) On Class III and nondesignated highways, the maximum is 73,280 lb. (i) On nondesignated highways, the single axle maximum is 18,000 lb, the tandem axle maximum is 32,000 lb, and the bridge formula does not apply. (j) On the Indiana Toll Road, the single axle maximum is 22,400 lb, the tandem axle maximum is 36,000 lb, and the maximum practical gross is 90,000 lb. (k) The maximum gross weight on Class AA highways is 62,000 lb, and on Class A highways, 44,000 lb. (l) Six- or seven-axle combinations are allowed 83,400 lb on the Interstate system, and 88,000 lb on other state highways. (m) A three-axle tractor hauling a tri-axle semitrailer has a maximum gross vehicle weight of 90,000 lb. (n) If the gross vehicle weight is less than 73,280 lb, the single axle maximum is 22,000 lb. (o) If the gross vehicle weight is 73,000 lb or less, the single axle maximum is 22,400 lb, and the tandem axle maximum is 36,000 lb. (p) Federal axle, gross and bridge formula limits apply to five-axle combinations if the gross vehicle weight is 80,000 lb or less. For other vehicles and gross vehicle weights over 80,000 lb other limits apply. State law sets axle weight controls which allow vehicles of legal overall length to gross a maximum of 164,000 lb. (q) Most city, county, and township roads are considered “9-ton routes” with a maximum gross vehicle weight of 73,280 lb. (r) On highways other than Interstate, primary, or other designated, the single axle maximum is 18,000 lb, the tandem axle maximum is 32,000 lb, the bridge formula is modified, and the gross vehicle weight maximum is 73,280 lb. (s) The maximum is directly controlled by the bridge formula. Given the state’s length laws, the maximum practical gross is 129,000 lb. (t) The five-axle “routine” permit value is estimated using a truck tractor-semitrailer with a 12,500 lb steering axle, a 47,250 lb drive tandem (five-ft spacing from State weight table), and a 50,400 lb spread tandem (8-ft spacing from the State weight table). (u) A determination is made on a case-by-case basis. (v) All “routine” permit values are calculated using 10-in wide tires and a maximum 800 lb/in of tire width loading value. (w) The five-axle “routine” permit value is estimated using a truck tractor-semitrailer with two 46,000 lb tandems plus a 12,000 lb steering axle. (x) If the gross vehicle weight is less than 71,000 lb, the single axle maximum is 22,400 lb, the tandem axle maximum is 36,000 lb, and a modified bridge formula applies. (y) If the gross vehicle weight is 73,280 lb or less, the single axle maximum is 22,400 lb, the tandem axle maximum is 36,000 lb, and the bridge formula does not apply. (z) If the gross vehicle weight is 75,185 lb or less, the tandem-axle maximum is 35,200 lb, and the bridge formula does not apply. (aa) The five-axle “routine” permit value is estimated using a truck tractor-semitrailer with two 52,000 lb tandems plus a 12,000 lb steering axle. (bb) The five-axle “routine” permit value is estimated using a truck tractor-semitrailer with a 13,000 lb steering axle, a 45,000 lb drive tandem, and a 48,125 lb spread tandem. Both tandem weight values are from the State weight chart. (cc) The five-axle “routine” permit value is estimated using a truck tractor-semitrailer with two 48,000 lb tandems plus a 12,000 lb steering axle. (dd) The maximum gross vehicle weight on nondesignated state highways is 73,500 lb, and on county roads 65,000 lb.

8TABLE 2 Maximum semitrailer lengths by state in 1994 (5) National network (NN) Other state highways State Trailer length (ft-in) Kingpin restrictions (ft-in) Trailer length (ft-in) Kingpin restrictions (ft-in) Overall length (ft-in) Alabama 57-0 41-0 KCRA(a) 53-0 Alaska 48-0 45-0 70-0 Arizona 57-6(g) 53-0 65-0 Arkansas 53-6 40-0 KCRTA(h) 53-6 California 53-0 38-0 KCSRA(i) 53-0 Same as NN Colorado 57-4 57-4 Connecticut 53-0 48-0 Delaware 53-0 53-0 60-0 Dist. of Col. 48-0 41-0 KCRT(b) 48-0 55-0 Florida 53-0 53-0 41-0 KCRT Georgia 53-0 41-0 KCRT 53-0 41-0 KCRT 67-6 Hawaii No Limit 45-0 60-0 Idaho 53-0 48-0 39-0 KCRA Illinois 53-0 42-6 KCRA 53-0 42-0 KCRA Indiana 53-0 40-6 KCRA 53-0 40-6 KCRA Iowa 53-0 53-0 40-0 KCRA 60-0 Kansas 59-6 59-6 Kentucky 53-0 No Limit 57-9 Louisiana 59-6 No Limit 65-0 Maine 53-0(c) 43-0 53-0 65-0 Maryland 53-0(d) 41-0 KCRT 53-0 41-0 KCRT Massachusetts 53-0(e) 53-0 Michigan 53-0 41-0 KCRT 50-0 Minnesota 53-0 41-0 KCRT 53-0 41-0 KCRT Mississippi 53-0 53-0 Missouri 53-0(d) No Limit 60-0 Montana 53-0 53-0 Nebraska 53-0 53-0 Nevada 53-0 53-0 70-0 New Hampshire 53-0(f) 41-0 KCRT 53-0 41-0 KCRT New Jersey 53-0 41-0 KCRT 53-0 41-0 KCRT New Mexico 57-6 No Limit 65-0 New York 53-0(d) 41-0 KCRT 48-0 65-0 North Carolina 53-0 41-0 KCRT No Limit 60-0 North Dakota 53-0 53-0 Ohio 53-0 53-0 Oklahoma 59-6 59-6 Oregon 53-0 Varies Pennsylvania 53-0 No Limit 60-0 Puerto Rico 48-0 Rhode Island 48-6 48-6 South Carolina 53-0 41-0 KCRT 48-0 South Dakota 53-0 53-0 Tennessee 53-0 41-0 KCRT 53-0 41-0 KCRT Texas 59-0 59-0 Utah 53-0 40-6 KCRT 53-0 40-6 KCRT Vermont 53-0(d) 41-0 KCRT 48-0 60-0 Virginia 53-0 37-0 Last tractor axle to first trailer axle No Limit 60-0 Washington 53-0 53-0 West Virginia 53-0 Same as VA No Limit 60-0 Wisconsin 53-0 41-0 KCRT No Limit 60-0 Wyoming 60-0 60-0 FOOTNOTES: (a) KCRA = Kingpin to center of rear axle (b) KCRT = Kingpin to center of rear tandem (c) permit may be required (d) Interstate and designated State routes (e) Requires annual letter of authorization; does not apply on the Massachusetts Turnpike (f) Designated routes (g) Only on Interstate system (h) KCRTA = Kingpin to center of rearmost tandem axle (i) KCSRA = Kingpin to center of single rear axle

NAFTA SIZE AND WEIGHT LIMITS AND PERFORMANCE CRITERIA The North American Free Trade Agreement (NAFTA), which went into effect in 1994, is an international treaty that calls for gradual removal of tariffs and other trade barriers on most goods produced and sold in North America. NAFTA forms the world’s second largest free-trade zone, bringing together 365 million consumers in Canada, Mexico, and the United States. An important part of NAFTA is the movement of goods by truck between Canada, Mexico, and the United States. The agreement contemplates free movement of Canadian and Mexican trucks to and from freight destinations in the United States and free transit of trucks from Canada to Mexico, and vice versa, through the United States. Implementation of NAFTA has the potential to change the mix of truck types on U.S. highways and may, therefore, have implications for geo- metric design of highways. Currently, Mexican trucks are generally limited to com- mercial areas along the U.S.-Mexican border. In fact, the vast majority of current trucking across the U.S.-Mexican border consists of drayage operations in which a trailer is moved from an industrial facility or terminal on one side of the bor- der to another industrial facility or terminal not far away on the other side of the border. Mexican trailers that move far- ther into the United States would then be pulled by a tractor operated by a U.S. trucker. NAFTA contemplated that the Mexican trucks would grad- ually be permitted to operate beyond the commercial areas along the border, first throughout the four border states (Cal- ifornia, Arizona, New Mexico, and Texas), and then through- out the United States. This has not happened yet; concerns have been raised about the safety of Mexican trucks, the finan- 9 cial responsibility of Mexican trucking firms, and domestic security. The Mexican government has lodged a formal com- plaint under NAFTA that the U.S. border should be opened to Mexican trucks, and a NAFTA Arbitral Panel has so ordered. Discussions continue concerning the date on which and the conditions under which Mexican trucks should have freer access to the United States. To consider the implications for geometric design of Canadian and Mexican trucks entering the United States, the research team has investigated current truck size and weight restrictions in Canada and Mexico and the size, weight, and performance restrictions that would apply to international trucks entering the United States. Table 4 compares current U.S., Canadian, and Mexican size and weight limits. This table applies to normal opera- tions within each country, not to international operations. Tables 5, 6, and 7 present more detailed current data on max- imum legal lengths and maximum legal weights of trucks operating within Mexico. The tables concerning Mexican truck characteristics refer to two road types. Type B roads in Mexico are those that compose the primary road network and that, given their geometric and structural characteristics, serve interstate commerce as well as providing continuity in vehic- ular flows. Type A roads are a higher class of road than Type B and include roads that will accommodate the high- est limits of size, capacity, and weight. Table 8 presents com- parable data for trucks operating in Canada based on the interprovincial Memorandum of Understanding (6). Two key NAFTA-related documents that deal with truck configuration issues are as follows: • Performance Criteria in Support of Vehicle Weight and Dimension Regulations: Background Paper, Draft 1, October 1998 (7). TABLE 3 Long combination vehicle weight limits by state (5) Gross vehicle weight limit (lb) Truck tractor and two trailing units Truck tractor and three trailing units 86,400 NM 90,000 OK OK 95,000 NE 105,500 ID, ND, OR, WA ID, ND, OR 110,000 CO CO 111,000 AZ 115,000 OH 117,000 WY 120,000 KS, MO(a) 123,500 AZ 127,400 IN, MA, OH IN 129,000 NV, SD, UT NV, SD, UT 131,060 MT 137,800 MT 143,000 NY 164,000 MI (a) From Kansas, within 20 miles of border. SOURCE: Final Rule on LCVs published in the Federal Register at 59 FR 30392 on June 13, 1994.

10 TABLE 4 Comparison of truck size and weight limits in the U.S., Canada, and Mexico (5) Characteristic U.S. Canada Mexico Steering axle weight limit (lb) N/A 12,125 14,320 Single axle weight limit (lb) 20,000 N/A 22,026 Tandem axle weight limit (lb) 34,000 37,479 39,647 Tridem axle weight limit (lb) – 46,297 to 55,000(a) 49,559 Gross vehicle weight limit (lb) 80,000 (Federal) (more for LCVs where allowed) 140,000(b) 146,476 Width limit (ft) 8.5 8.5 8.5 Semitrailer length limit (ft) 48 (53 common) 53 N/A Vehicle length limit (ft) N/A 82.0 68.2 (semi) 101.7 (double) King-pin to rear axle distance (ft) N/A Control limits N/A Minimum interaxle spacings N/A Yes Yes (a) In eastern Canada. (b) In Ontario and far western Canada. TABLE 5 Maximum legal length of trucks in Mexico by class of vehicle and type of road Maximum legal length (ft) / (meters) Class of vehicle Type A Type B Bus 45.90 (14.00) 45.90 (14.00) SU Truck with six or more tires 45.90 (14.00) 45.90 (14.00) SU Truck and trailer 93.44 (28.50) 93.44 (28.50) Tractor semitrailer 68.20 (20.80) 68.20 (20.80) Tractor semitrailer-trailer 101.60 (31.00) 93.44 (28.50) Tractor semitrailer-semitrailer 81.97 (25.00) 81.97 (25.00) SOURCE: Dr. Alberto Mendoza, Mexican Transportation Institute TABLE 6 Maximum legal weight of trucks in Mexico by type and number of axles for highways of Types A and B Axle configuration Weight, lb (metric tonnes) Single axle with two tires 14,320 (6.50) Single axle with four tires 22,026 (10.00) Power single axle with four tires 24,229 (11.00) Power double axle or tandem with six tires 34,140 (15.50) Double or tandem with eight tires 39,647 (18.00) Power double axle or tandem with eight tires 42,951 (19.50) Triple or tridem with twelve tires 49,559 (22.50) SOURCE: Dr. Alberto Mendoza, Mexican Transportation Institute

11 • Highway Safety Performance Criteria in Support of Vehi- cle Weight and Dimension Regulations: Candidate Cri- teria and Recommended Thresholds, October 1999 (8). No formal agreement on size and weight limits for inter- national trucks has yet been reached, but the following lim- its have been recommended by the NAFTA Land Trans- portation Standards Subcommittee for trucks on highways that will constitute the International Access Network (IAN): • Height—4.15 m [13.6 ft] • Width—2.6 m [102.4 in] • Overall Length—23.0 m [75.5-ft] for tractor-semitrailer combinations 25.0 m [82.0-ft] for double-trailer combinations • Box Length—16.2 m [53.2-ft] for trailer-semitrailer combinations 20.0 m [65.6-ft] for double-trailer com- binations • Transient Low-Speed Offtracking—No more than 5.6-m [18.3-ft] offtracking in a 90-degree turn of 14.0-m [45.9-ft] radius • Front Swingout—No more than 0.45-m [18-in] front swingout in a 90-degree turn of 14.0-m [45.9-ft] radius • Rear Swingout—No more than 0.20-m [8-in] rear swingout in a 90-degree turn of 14.0-m [45.9-ft] radius • Load Transfer Ratio—Acceptable maximum of 0.60 • Transient High-Speed Offtracking—Acceptable maxi- mum of 0.8-m [32-in] The overall length and box length are defined in Figure 1. The issues of transient low-speed offtracking, front swingout, rear swingout, load transfer ratio, and transient high-speed offtracking are defined and discussed in Chapter 5 of this report. These IAN criteria are similar to current U.S. size and weight restrictions with the following exceptions: TABLE 8 Maximum truck dimensions specified in Canadian Interprovincial Memorandum of Understanding (6) Maximum dimension, m [ft] Vehicle category Overall length Overall width Overall height Box length 1—Tractor-semitrailer 23.0 [75.4] 2.6 [8.5] 4.15 [13.6] 16.2 [53.8] 2—A-train double(a) 25.0 [82.0] 2.6 [8.5] 4.15 [13.6] 18.5 [60.7](d) 3—B-train double(b) 25.0 [82.0] 2.6 [8.5] 4.15 [13.6] 20.0 [65.6](d) 4—C-train double(c) 25.0 [82.0] 2.6 [8.5] 4.15 [13.6] 20.0 [65.6](d) 5—Straight truck 12.5 [41.0] 2.6 [8.5] 4.15 [13.6] not controlled 6—Straight truck with pony trailer 23.0 [75.4] 2.6 [8.5] 4.15 [13.6] 20.0 [65.6](e) 7—Straight truck with full trailer 23.0 [75.4] 2.6 [8.5] 4.15 [13.6] 20.0 [65.6](e) (a) Tractor/semitrailer/full trailer with conventional single-hitch connection. (b) Tractor/semitrailer/semitrailer with converter dolly such that both trailers are semitrailers. (c) Tractor/semitrailer/full trailer with double drawbar dolly. (d) Combined length of both trailer cargo areas and the space between them. (e) Combined length of the truck cargo area, the trailer cargo area, and the space between them. TABLE 7 Maximum legal weight of trucks in Mexico by type of vehicle for highways of Types A and B Vehicle class Designation No. of tires GVW, lb (metric tonnes) B2 6 38,546 (17.50) B3 8 48,458 (22.00) B3 10 57,268 (26.00) Bus B4 10 67,180 (30.50) C2 6 38,546 (17.50) C3 8 48,458 (22.00) Single Unit Truck C3 10 57,268 (26.00) C2 – R2 14 82,599 (37.50) C2 – R3 18 100,220 (45.50) C3 – R2 18 101,321 (46.00) Truck-Trailer Combination C3 – R3 22 118,942 (54.00) T2 – S1 10 60,572 (27.50) T2 – S2 14 78,193 (35.50) T3 – S2 18 96,916 (44.00) Tractor-Semitrailer T3 – S3 22 160,828 (48.50) T2 – S1 – R2 18 104,625 (47.50) T3 – S1 – R2 22 123,348 (56.00) T3 – S2 – R2 26 133,260 (60.50) T3 – S2 – R3 30 138,766 (63.00) Tractor-Semitrailer- Trailer T3 – S2 – R4 34 146,475 (66.50) Tractor-Semitrailer- Semitrailer T3 – S3 – S2 30 132,158 (60.00) SOURCE: Dr. Alberto Mendoza, Mexican Transportation Institute

• Overall length limitations are included. Currently, trucks on the NN in the United States are not subject to over- all length limits, only limits on trailer lengths. How- ever, overall length limits are included because most truck travel in Canada and Mexico is on two-lane high- ways where overall length may restrict the ability to pass a truck. • The box length limit for tractor-semitrailer combinations is consistent with the 16.2-m [53-ft] trailers that are used extensively in the United States. The 20.0-m [65.6-ft] 12 limit for double-trailers is consistent with combinations with two 8.7-m [28.5-ft] trailers, which are currently the most widely used in the United States. • Explicit regulation of transient low-speed offtracking and rear swingout is rare in the United States. Many states address this indirectly by regulating the kingpin to rearaxle distance and/or the rear overhang distance. • Regulation of front swingout, load transfer ratio, and transient high-speed offtracking is currently rare or nonexistent in the United States. Wheelbase Box Length KCRT KCRA Overall Length Box Length Overall Length Wheelbase Figure 1. Definition of truck dimensions.