State Bridge Load Posting Processes and Practices (2014)

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27 chapter three METHODS OF EVALUATION OF WEIGHT LIMITS FOR BRIDGES AND CULVERTS Chapter three presents details on the legal loads, overweight permit loads, methods of load rating, load rating vehicles, and posting levels used by U.S. states. It reports on research in states related to load posting. There are limits in law and in regulation on the weights of vehicles that can cross highway bridges and culverts. Bridges and culverts are posted for load when safe load capacity is less than legal loads and routine permit loads. Legal Loads Legal loads are established in federal regula- tion, in state law, and in local law. Federal reg- ulation of loads applies to interstate highways, state law to other highways generally, and local law to roads owned by local government. Load limits for highway bridges and culverts are expressed as limits on axle loads, on tandem- axle loads, and vehicle gross weights. Federal limits, apart from exclusions and exemptions, are 20,000 lb for single axles, 34,000 for tan- dem axles, and 80,000 for GVW. Legal loads in 32 states exceed one or more of the limits set in federal regulation. Information on legal loads is presented for 50 U.S. states. Overweight Permit Loads Vehicles that exceed load limits in federal regulation or in state law routinely travel on highways. This includes vehicles protected by grandfather provisions in federal regulation, longer combination vehicles named as excep- tions in federal regulation, vehicles exempt from state law for specific commodities or spe- cific uses, and vehicles that qualify for over- weight permits. Information on overweight permit loads is presented for 43 survey states. Load Rating Methods States evaluate their bridges and culverts for capacity to carry legal vehicles, exempt vehi- cles, and overweight permit vehicles. Load ratings, the numerical outcomes of evalua- tions, indicate whether posting for load are needed. All states apply computational struc- tural analysis in load ratings. Approximate structural analysis using live load distribu- tion factors is the most common approach. Refined methods of structural analysis using three-dimensional models of structures are used for complex bridges and for structures that might be posted for load if approximate analysis alone is used. Load ratings are set using allowable stress basis, load factor basis, or load and resistance factor basis. These bases follow from meth- ods for design of bridges and culverts. Weight Limits for Load Posting Weight limits for load posted structures are set at or below operating ratings; the esti- mates of maximum single vehicle loads that structures can carry without damage. Some states post structures at loads less than operat- ing ratings if structural condition is poor. Spe- cific weight limits for posted structures can depend on structure condition, ADT, detour length, load path redundancy, and the level of enforcement of weight limits. Components to Rate for Load Evaluations of safe load capacity of struc- ture always include superstructure com- ponents, and may include bridge decks and substructures depending on conditions of decks and substructures, and on the conse- quence that could follow from overload of these components. Load Rating Vehicles Computational methods for load rating use numerical descriptions of vehicles. These rat- ing vehicles are expressed as counts, spacings, and weights of axles. Thirty-three survey states use AASHTO vehicles in load rating. Thirty- two survey states define additional rating vehi- cles for legal loads. Condition of Components Deterioration in components of structures is included in computations for load rating through field measurement of remaining sections (41 survey states), and through AASHTO’s condition factor, jC (18 survey states). Research in Load Posting Current research related to load posting includes use of weigh-in-motion (WIM) data to characterize truck loads and to evaluate

28 States establish load limits for single axles, tandem axles, and GVW. States generally adopt the limits set in USC Title 23 for interstate highways, including grandfathered provisions and exceptions for weight limits for some vehicles or route segments. Some states set other, higher limits for non-interstate highways such as U.S.-numbered routes and state highways. Separate still are roads owned and maintained by counties, cities, and other local governments. These governments can set their own limits on load. States’ legal axle loads, tandem-axle loads, and GVW are collected from state statutes, state administrative codes, and from a U.S.DOT study of truck size and weight (88). These are the legal loads for non-interstate highways. Bridges and culverts are posted when load capacity is not adequate for these legal loads. States’ Legal Single-Axle Loads Thirty-six of 50 states set limits for axle load at 20,000 lb, the limit set in USC Title 23 (Table 46). Fourteen states set higher limits on axle load, with the highest being 24,000 lb. No state sets the limit on single-axle load less than 20,000 lb. States’ Legal Tandem-Axle Loads Thirty-three of 50 states set limits for load on tandem axles equal to 34,000 lb, the limit set in USC Title 23 (Table 47). Seventeen states set higher limits for tandem-axle load. The highest limit is 48,000 lb. No state sets limits below 34,000 lb for tandem axles. multiple presence factors, calibration of refined models for structural analysis, devel- opment of load rating methods for complex bridges, and evaluation of load effects of spe- cial vehicles on bridges. LEGAL LOADS For interstate routes, U.S. Code Title 23 (87) sets limits on axle load, tandem-axle load, and GVW. The general limits in Title 23 are 20,000 lb for single-axle load, 34,000 lb for tandem-axle load, and 80,000 lb for GVW. In addition, combined weight W of axle groups must not exceed limits in pounds related to the number of axles N and the wheelbase of the outermost axles L in feet. This is the federal bridge gross weight formula. W LNN N( )= − + +500 1 12 36 (1) Title 23 admits exceptions to the general limits on load. States’ legal loads that were in effect on July 1, 1956, remain legal today under a grandfathering provision. Other exceptions have been written into Title 23. Among these are exceptions for loads traveling on designated route segments, and excep- tions for longer combination vehicles (LCVs). Title 23 lists LCV exceptions for 22 states. Weights of LCVs range from 86,400 lb to 164,000 lb (Table 45). LCV exceptions are: (1) legal under federal regulation for operation on interstate highways; (2) state-specific; and (3) subject to state law on vehicle weight and dimensions. In 18 of 22 states, the LCVs listed in Title 23 require state-issued overweight or over- dimension permits. TABLE 45 USC TITLE 23 WEIGHT EXCEPTIONS FOR LCVs State GVW, lb Permit Required State GVW, lb Permit Required Arizona 129,000 Y Nevada 129,000 Y Colorado 110,000 Y New Mexico 86,400 N Idaho 105,500 Y New York 143,000 Y Indiana 127,400 Y1 North Dakota 105,500 Y Iowa2 129,000 N Ohio 127,400 Y Kansas 120,000 N3 Oklahoma 90,000 Y Massachusetts 127,400 Y Oregon 105,500 Y Michigan 164,000 N South Dakota 129,000 Y Missouri 120,000 Y Utah 129,000 Y Montana 137,800 Y Washington 105,500 Y Nebraska 95,000 Y Wyoming 117,000 N 1Indiana DOT furnishes free annual tandem-trailer permits. 2Restricted to portions of I-29 and I-129 within corporate limits of Sioux City, Iowa. 3Permit not required for travel on Kansas Turnpike. Permit is needed to reach some motor freight terminals in Kansas.

29 TABLE 46 LEGAL SINGLE AXLE LOADS, NON-INTERSTATE HIGHWAYS State Axle Load, k State Axle Load, k State Axle Load, k Alabama 20 (7) Louisiana 20 (96) Ohio 20 (73) Alaska 20 (89) Maine 22.4 (63) Oklahoma 20 (107) Arizona 20 (53) Maryland 22.4 (10) Oregon 20 (74) Arkansas 20 (88) Massachusetts 24 (97) Pennsylvania 22.4 (108) California 20 (90) Michigan 20 (98) Rhode Island 22.4 (88) Colorado 20 (54) Minnesota 20 (99) South Carolina 20 (88) Connecticut 22.4 (88) Mississippi 20 (100) South Dakota 20 (75) Delaware 22.4 (55) Missouri 20 (101) Tennessee 20 (109) Florida 20 (91) Montana 20 (102) Texas 20 (76) Georgia 18 (57) Nebraska 20 (103) Utah 20 (77) Hawaii 22.5 (92) Nevada 20 (104) Vermont 22.4 (88) Idaho 20 (58) New Hampshire 20 (13) Virginia 20 (78) Illinois 20 (9) New Jersey 22.4 (88) Washington 20 (79) Indiana 20 (93) New Mexico 21.6 (105) West Virginia 20 (110) Iowa 20 (60) New York 22.4 (70) Wisconsin 20 (81) Kansas 20 (94) North Carolina 21 (106) Wyoming 20 (111) Kentucky 20 (95) North Dakota 20 (72) TABLE 47 LEGAL TANDEM AXLE LOADS, NON-INTERSTATE HIGHWAYS State Tandem Axle, k State Tandem Axle, k State Tandem Axle, k Alabama 34 (7) Louisiana 34 (96) Ohio 34 (73) Alaska 38d (89) Maine 41b (63) Oklahoma 40 (107) Arizona 34 (53) Maryland 34 (10) Oregon 34 (74) Arkansas 34 (88) Massachusetts 34 (97) Pennsylvania 40.4e (108) California 34 (90) Michigan 34 (98) Rhode Island 36b (114) Colorado 40a (54) Minnesota 34 (99) South Carolina 36b (115) Connecticut 36e (88) Mississippi 34 (100) South Dakota 34 (75) Delaware 40b (55) Missouri 34 (101) Tennessee 34 (109) Florida 34 (91) Montana 34 (102) Texas 34 (76) Georgia 40.68b (57) Nebraska 34 (103) Utah 34 (77) Hawaii 34 (92) Nevada 34 (113) Vermont 36a (116) Idaho 34 (58) New Hampshire 36b (13) Virginia 34 (78) Illinois 34 (9) New Jersey 34 (88) Washington 34 (79) Indiana 34 (93) New Mexico 37.44f (105) West Virginia 34 (117) Iowa 34 (112) New York 34 (70) Wisconsin 34 (81) Kansas 34 (94) North Carolina 38b (106) Wyoming 36c (111) Kentucky 34 (95) North Dakota 48c (72) aAxle spacing not specified. bAxle spacing 3’-4” minimum. cAxle spacing greater than 3’-4”. dAxle spacing 3’-6” minimum. eAxle spacing 6’ minimum. fAxle spacing 8’ minimum.

30 bridge formulas allow greater GVW than the federal bridge formula. Exempt Vehicles States exempt specific vehicles from some limits on load. Vehicles are exempt for specific uses, specific commodities, or specific owners. Exempt uses include off-road equipment for construction or for husbandry. Exempt commodities include agricultural products, raw forest products, refuse, construction materials, and products used for manufacture such as steel coil or ingot. Also exempt are manufactured items such as machin- ery, equipment, boats, and prefabricated homes that, as part of States’ Legal Gross Vehicles Weights Thirty-two states set limits for GVW equal to 80,000 lb, the limit set in USC Title 23 (Table 48). Nine states set GVW limits greater than 100,000 lb. The greatest limit is 164,000 lb. No state set a limit for GVW of less than 80,000 lb. States’ Legal Loads—Bridge Formulas States set limits on GVW in relation to axle count and wheel- base using the federal bridge formula or using state-specific bridge formulas (Table 49). State-specific formulas are com- pared with the federal formula in Table 50. All state-specific TABLE 48 LEGAL GVW LOADS, NON-INTERSTATE HIGHWAYS State GVW, kips State GVW, kips State GVW, kips Alabama 80 (7) Louisiana 88 (96) Ohio 80 (73) Alaska 90 (88) Maine 100 (63) Oklahoma 90 (121) Arizona 80 (53) Maryland 80 (10) Oregon 80 (74) Arkansas 80 (88) Massachusetts 80 (97) Pennsylvania 80 (108) California 80 (90) Michigan 164 (119) Rhode Island 80 (88) Colorado 85 (54) Minnesota 80 (99) South Carolina 80 (88) Connecticut 80 (88) Mississippi 80 (100) South Dakota 155.5 (122) Delaware 80 (55) Missouri 80 (101) Tennessee 80 (109) Florida 80 (91) Montana 137.8 (120) Texas 80 (76) Georgia 80 (57) Nebraska 95 (103) Utah 80 (77) Hawaii 88 (92) Nevada 129 (113) Vermont 80 (88) Idaho 129 (118) New Hampshire 80 (13) Virginia 80 (78) Illinois 80 (9) New Jersey 80 (88) Washington 115 (79) Indiana 80 (93) New Mexico 86.4 (105) West Virginia 80 (110) Iowa 96 (112) New York 80 (70) Wisconsin 80 (81) Kansas 85.5 (94) North Carolina 80 (106) Wyoming 117 (111) Kentucky 80 (95) North Dakota 105.5 (72) TABLE 49 STATES’ BRIDGE FORMULAS State GVW Formula Note California (123) Truck cranes, Purple route Truck cranes, Green route Colorado (54) 85,000 lb max. Hawaii (92) non-interstate, 88,000 lb max. New York (70) 71,000 lb max. Washington (79) 7 ft < 10 ft 105,500 lb max. 10 ft wheelbase < 30 ft wheelbase 105,500 lb max. wheelbase 30 ft 105,500 lb max. W = Gross vehicle weight in pounds. L = Wheelbase in feet. N = Count of axles.

31 their production, must be moved among sites. Exempt own- ers are public utilities and government agencies such as fire departments. Table 51 lists categories of exempt vehicles and loads. The terms used in “Examples” are taken from state stat- utes. Many terms overlap. Similar but non-identical terms are kept to show the variations among statutes. Table 52 lists exemptions for axle load greater than 20,000 lb. The greatest exempt axle load is 32,000 lb. Table 53 lists exemptions for tandem-axle load greater than 34,000 lb. The greatest exempt tandem-axle load is 50,000 lb. Table 54 lists exemptions for GVW greater than 80,000 lb. The greatest exempt GVW is 99,000 lb. A detailed list of exempt vehicles and loads is in Table B3. Formula Axles Wheelbase, ft GVW, LB USC Title 23 4 57 80,000 California Purple Route 108,850 California Green Route 94,270 Colorado 97,000 Hawaii 87,300 New York 91,000 Washington 105,500 TABLE 50 COMPARISON OF BRIDGE FORMULAS TABLE 51 SUMMARY—EXEMPT VEHICLES Exempt Vehicles States Group Examples Agriculture Agricultural equipment, agricultural products, animal waste, bulk milk, chile pepper modules, cotton harvest, cotton modules, cotton seed or equipment, crops, dairy products/supplies, farm implements, fertilizer, fuel, live poultry, livestock, meats, pesticides, rendering materials, seeds, water Alabama, California, Delaware, Georgia, Idaho, Illinois, Indiana, Iowa, Louisiana, Maine, Minnesota, Mississippi, Montana, North Carolina, North Dakota, Oklahoma, Oregon, South Dakota, Tennessee, Texas, Utah, Washington, Wisconsin, Wyoming Construction Cranes, concrete, concrete pump truck, concrete products, concrete ready-mix truck, dump trucks, unhardened ready-mix concrete, highway construction and maintenance equipment, highway improvement vehicles Alabama, California, Florida, Georgia, Illinois, Iowa, Louisiana, Maine, Maryland, Mississippi, North Carolina, Texas, Utah, Washington Fire Fighting Fire department vehicle, firefighting apparatus Delaware, Iowa, Maine, North Carolina, Texas, Utah, Washington Forest Products Bark, Christmas trees, knuckle boom log loaders, logs, log haulers, lumber, piling, poles, pulpwood, sawdust, sawn logs, stull, timber, tree-length poles, vehicles transporting logs or poles from forest to sawmill, wood chips, wood residuals California, Georgia, Idaho, Indiana, Louisiana, Maine, Michigan, Minnesota, Mississippi, Montana, North Carolina, Oklahoma, South Dakota, Tennessee, Texas, Utah, Wisconsin, Wyoming Materials Aggregates, asphalt millings, bulk liquid commodities, bulk rock, bulk soil, concentrates (ores), ores, sand, scrap metal Georgia, Idaho, Louisiana, Maine, North Carolina, Oklahoma, Tennessee, Wisconsin, Wyoming Misc. Bus, public utility truck, seagoing container, state- or municipally owned vehicle, utility truck California, Colorado, Illinois, Iowa, Maine, Maryland, Minnesota, New York, Oklahoma Refuse Garbage hauler, garbage operations, garbage trucks, recyclable materials, recycling operations, refuse operations, septage, solid waste California, Georgia, Illinois, Indiana, Maine, Mississippi, North Carolina, Oklahoma, Oregon, Tennessee, Texas, Washington, Wisconsin Towing Towing, tow trucks, towing vehicles under emergency conditions Illinois, Utah, Washington

32 cles, and direct permit holders to use these routes. State inven- tories of bridges and culverts are seen to have three classes of structures; structures that can carry permitted overweight vehicles, structures that can carry legal loads only, and struc- tures, posted for load, that cannot carry full legal loads. Overweight permits can allow single trips or multiple trips by overweight vehicles. Routine permits are multi-trip per- mits. Routine permits are also called annual permits, blanket permits, extended trip permits, and continuous trip permits. Routine permits allow overweight vehicles to mix in normal traffic and travel at normal speeds. Permits are limited to des- ignated routes, and may be restricted in their hours of operation or excluded from travel on certain days (e.g., federal holidays). Overweight permits and the permitting procedures of states provide higher levels of scrutiny and control of overweight OVERWEIGHT PERMIT LOADS States issue overweight permits for some vehicles that exceed legal limits on axle load, tandem-axle load, or GVW. USC Title 23 restricts states’ issuance of overweight permits for travel on interstate highways. States can issue overweight per- mits for non-divisible loads and for specific LCVs named in Title 23. Title 23 does not constrain issuance of overweight permits for travel on non-interstate highways. For truckers, states publish guidance on the overweight permits that are available. State publications show loads and vehicle configurations as the counts, weights, and spacings of axles that qualify for permits. States have evaluated their bridges and culverts for these published configurations of overweight vehicles. This is an application of load rating. States identify routes that are able to carry overweight vehi- TABLE 52 EXEMPT VEHICLES—AXLE LOAD GREATER THAN 20,000 POUNDS State Configuration Load (lb) Colorado (54) Utility truck 21,000 Georgia (57) Live poultry, cotton, feed, poultry waste, construction aggregates, unhardened concrete, forest products, granite, raw ore or mineral, solid waste or recovered materials 23,000 Illinois (9) Rendering materials, garbage, refuse, or recycling operations 22,000 Indiana (93) Garbage truck 24,000 Iowa (60) Fence-line feeder, grain cart, or tank wagon, 28,000 Maine (63) Dump trucks, concrete ready-mix trucks, raw ore, refrigerated products 24,200 Maryland (10) Seagoing container 22,400 Nevada (104) Mass transit 25,000 New York (70) State- or municipally owned vehicle 32,000 North Carolina (106) Agriculture crop, water, fertilizer, pesticides, seeds, fuel, or animal waste, meats, livestock or live poultry, unhardened ready-mixed concrete, forest products, wood residuals, raw logs, Christmas trees, firefighting apparatus, bulk soil, bulk rock, sand, sand rock, or asphalt millings 22,000 Garbage hauler 23,500 5+ axles, agriculture crop, water, fertilizer, pesticides, seeds, fuel, or animal waste, meats, livestock or live poultry, forest products, wood residuals, raw logs, Christmas trees 26,000 North Dakota (72) Agricultural equipment 22,000 Oregon (74) Garbage or refuse operations 22,000 Tennessee (109) Farm trucks and machinery, logging, sand, coal, clay, shale, phosphate, solid waste, recovered materials 22,000 Texas (76) Transporting recyclable materials 21,000 Concrete ready-mix truck, concrete pump truck 23,000 Washington (79) Firefighting apparatus 24,000 Wisconsin (81) Dairy products/supplies 21,000

State Configuration Load (lb) Georgia (57) Live poultry, cotton, feed, poultry waste, unhardened concrete, construction aggregates, forest, granite, raw ore or mineral products, solid waste or recovered materials 46,000 Idaho (58) Unprocessed agricultural products including livestock, logs, pulpwood, stull, poles or piling, ores, concentrates, sand and gravel, aggregates 37,800 Illinois (9) Collection of rendering materials 40,000 Indiana (93) Garbage truck 42,000 Maine (63) Dump trucks, concrete ready-mix trucks, raw ore, refrigerated products 46,000 Maryland (10) Seagoing container 44,000 Nevada (104) Refuse 40,000 New York (70) State- or municipally owned vehicle 42,000 North Carolina (106) Agriculture crop, water, fertilizer, pesticides, seeds, fuel, or animal waste, meats, livestock or live poultry, firefighting apparatus, forest products, wood residuals, raw logs, Christmas trees, bulk soil, bulk rock, sand, sand rock, or asphalt millings 42,000 5+ axles, agriculture crop, water, fertilizer, pesticides, seeds, fuel, or animal waste, meats, livestock, or live poultry, forest products, wood residuals, raw logs, Christmas trees 44,000 Unhardened ready-mixed concrete 46,000 Cotton seed 50,000 Oregon (74) Farm vehicle, 10-ft wheelbase 37,800 Tennessee (109) Farm trucks and machinery, logging, sand, coal, clay, shale, phosphate, solid waste, recovered materials 37,400 Texas (76) Transporting recyclable materials 44,000 Concrete ready-mix truck, concrete pump truck 46,000 Utah (124) Hauling livestock or grain, GVW 80,000 lb 36,000 Washington (79) Firefighting apparatus 43,000 Wisconsin (81) Dairy products/supplies, forest products, scrap metal, septage 37,000 TABLE 53 EXEMPT VEHICLES—TANDEM AXLE LOAD GREATER THAN 34,000 POUNDS TABLE 54 EXEMPT VEHICLES—GVW GREATER THAN 80,000 POUNDS State Configuration Load (lb) Iowa (60) Implement of husbandry 96,000 Maine (149) Unprocessed milk, farm produce, dump trucks, ready-mix trucks, concrete products, building materials, forest products, raw ore, rock, soil, road salt, refrigerated products, incinerator ash, solid waste 100,000 Maryland (10) 6 axle, Garrett County 87,000 Seagoing container 90,000 Minnesota (99) Hauling livestock 88,000 Forest products 99,000 North Carolina (106) 5+ axles, agriculture crop, water, fertilizer, pesticides, seeds, fuel, or animal waste, meats, livestock or live poultry, firefighting apparatus, forest products, wood residuals, raw logs, Christmas trees 90,000 Oklahoma (121) Utility vehicle, 5 axles 85,500 Agricultural commodities, utility vehicle—6 axles, refuse—6 axles 90,000 Tennessee (109) Farm trucks and machinery logging, sand, coal, clay, shale, phosphate, solid waste, recovered materials 88,000

34 and can issue overweight permits without further analysis. These loads are “routine” from the perspective of the state bridge load rater. Overweight Permit Axle Loads Twenty-five survey states permit axle load for overweight vehicles in excess of 20,000 lb (Table 55). Six states permit overweight axle load at 40,000 lb or greater. The greatest overweight permit axle load is 65,000 lb. Some overweight permits for axles are restricted to specific commodities or for designated vehicles. vehicles as compared with legal loads. The state, through its DOT, examines load capacities of structures, and relates struc- tures and routes to configurations of overweight vehicles. Information on axle loads, tandem-axle loads, and GVW of overweight permit vehicles is collected from state statutes, states’ published policies on overweight permits, and pub- lished advice to truckers. These sources yield limits on loads, load tables showing GVW for various counts and spacings of axles, and configurations of overweight vehicles. Most, but not all, of these loads are allowed under routine permits. All of these loads are permitted without review of structures; states have already rated bridges and culverts for these loads, TABLE 55 OVERWEIGHT PERMIT LOADS—AXLE LOADS State Configuration Load (lb) Alabama (7) 22,000 Mining equipment, refractory grade bauxite 27,000 California (123) Orange route 21,000 Green route 26,000 Purple route 30,000 Florida (125) Map 3, blanket permit, truck cranes 22,000 Map 1 or 2, blanket permit, wreckers 25,000 Map 1 or 2, truck cranes 27,500 Map 2, wreckers 45,000 Georgia (126, 127) Wrecker emergency tow 21,000 Annual permit 25,000 Idaho (118) Yellow routes, single axle 22,500 Orange routes, single axle 24,000 Green routes, single axle 25,500 Blue routes, single axle 27,000 Purple routes, single axle 30,000 Black routes, single axle 33,000 Illinois (128) In tandem, limited continuous operations 26,000 Off-road equipment, 25 mile travel limit 30,000 Indiana (129) Extra heavy duty highway 65,000 Iowa (60) Crane 24,000 Implement of husbandry 25,000 Kansas (94) Annual permit 24,000 Kentucky (130) Self-propelled truck crane 23,000 24,000 Louisiana (131) Off-road equipment 30,000 Maryland (132) International freight 22,400 Michigan (133) Construction equipment 24,000 Minnesota (134) Refuse-compactor vehicles 22,000 Montana (122) 21,500 North Carolina (135) Annual permit 25,000 Self-propelled off-highway construction equipment 37,000

35 North Dakota (72) Trucks, combination vehicles 24,000 Cranes, truck-mounted equipment 30,000 Self-propelled workover rigs 30,000 Self-propelled workover rigs “SE” 31,200 Earthmoving equipment 52,000 Ohio (136) Permit vehicle 29,000 Oregon (137) Heavy haul weight 21,500 Utah (77) Annual permit, GVW < 125,000 29,500 Single trip, farm tractors, off-road construction equipment 40,000 Annual permit, trunnion, GVW < 125,000 60,000 Virginia (138) Permit vehicle 24,000 Washington (79) State highway 22,000 Washington (139) 8 tires, 8-ft axle width 24,725 8 tires, 10-ft axle width 26,875 8 tires, 12-ft axle width 29,025 8 tires, 16-ft axle width 43,000 West Virginia (80) Single trip permit 28,000 Wisconsin (27) Garbage, refuse, or scrap hauling 25,000 Annual permit 30,000 Rear axle, transporting an earthmover 35,000 Wyoming (111) Permit 25,000 TABLE 55 (continued) Overweight Permit Tandem Axles Twenty-three survey states permit tandem-axle load in excess of 34,000 lb for overweight vehicles (Table 56). Five states permit overweight tandem-axle load of 60,000 lb or greater. The greatest overweight permit tandem-axle load is 90,000 lb. Similar to overweight single-axle load, some overweight tandem-axle loads are restricted to specific commodities or for designated vehicles. Overweight Permit GVW Thirty-six survey states permit GVW for overweight vehi- cles in excess of 80,000 lb (Table 57). Nine states permit GVW for overweight vehicles at 200,000 lb or higher. The greatest GVW for overweight permit vehicles is 304,000 lb. Overweight vehicles at greater GVW might receive permits after analysis of bridges and culverts along proposed routes. LOAD RATING Load rating is the evaluation of safe load capacity of high- way structures. Two levels of load rating are reported to NBI: inventory rating and operating rating. The inventory rating is a lower bound on the safe load capacity of a structure. The operating rating is a maximum tolerable load for a structure. Load ratings are also computed as design load ratings, legal load ratings, and overweight permit vehicle ratings. Load ratings are computed for rating vehicles. A rating vehicle is a defined set of axle weights and axle spacings. Rating vehi- cles correspond variously to design loads, to legal loads, and to overweight permit vehicle loads. Load posting may be set at a structures’ operating rating, its inventory rating, or at an intermediate level between the inventory and operating ratings. Load Rating Methods Load rating methods include load rating by computation, by load test, or by field evaluation and engineering judg- ment. Load rating by computation uses a basis in Allowable Stress Rating (ASR), Load Factor Rating (LFR), or Load and Resistance Factor Rating (LRFR). A load rating for a structure can be expressed as a rating factor, RF. A rating factor is a scaling factor. RF is greater than 1 when a structure has capacity for load greater than a rating vehicle. RF is less than 1 when a structure has capac- ity for load less than a rating vehicle. AASHTO (5) provides equations for RF for use in computational load rating.

36 State Configuration Load (lb) California (123) Purple route 42,000 Green route 52,000 4 axle crane, Purple route 54,300 Orange route 60,000 Florida (125) Map 2 & Map 3 blanket permit, Map 3 truck cranes 44,000 Map 1 blanket permit, Map 1 wreckers 50,000 Map 1 truck cranes, Map 2 truck cranes 55,000 Map 2 wreckers 90,000 Georgia (127) Wrecker emergency tow 40,000 Idaho (58) Yellow routes 38,000 Orange routes 41,000 Green routes 43,500 Blue routes 46,000 Purple routes 51,500 Black routes 56,000 Illinois (9) 4 or more axles 44,000 5 or more axles 48,000 6 or more axles 60,000 Illinois (128) 3 axle, tractor 48,000 Truck crane or drill rig, 3 axle, 18-ft wheelbase 48,000 In tandem, limited continuous operations 50,000 3 axle, semi-trailer 60,000 Kansas (94) Annual permit 45,000 Special mobile equipment 49,000 Cotton modules 50,000 Kentucky (130) 5 axle vehicle 45,000 Self-propelled truck crane 46,000 6+ axle vehicle 48,000 Louisiana (131) Bagged rice 34,000 Bagged rice 37,000 Cotton modules 48,000 Off-road equipment 54,000 Maryland (10) International freight 44,000 Milk tank, forestry products 52,000 Minnesota (99) Refuse-compactor vehicles 38,000 Mississippi (100) Harvest permit, pre-package products 40,000 Missouri (101) Blanket permit, well drill rig, concrete pump truck 40,000 North Carolina (135) Annual permit 50,000 Self-propelled off-highway construction equipment 50,000 North Dakota (140) Trucks, combination vehicles 45,000 Cranes, truck-mounted equipment 50,000 Self-propelled workover rigs 50,000 Self-propelled workover rigs “SE” 52,000 TABLE 56 ROUTINE PERMIT LOADS—TANDEM AXLE LOADS

37 State Configuration Load (lb) Ohio (73) Spacing 4 ft 36,000 Spacing 16 ft 50,000 Oklahoma (141) Annual envelope permit 40,000 Oregon (137) Heavy haul weight 43,000 Washington (79) Permit vehicle 43,000 West Virginia (80) Single trip permit 45,000 Wisconsin (142) Garbage, refuse, or scrap hauling permits 42,000 Annual permit 60,000 Wyoming (111) Class B or C Permit 55,000 TABLE 56 (continued) TABLE 57 ROUTINE OVERWEIGHT PERMIT LOADS—GVW State Configuration Load (lb) Alabama (7) Permit vehicle 150,000 Arizona (143, 144) Within 20 miles of state border 111,000 9 axles 121,000 10 axles 123,500 Vehicle hauling a houseboat 150,000 Envelope permit, non-reducible load 250,000 California (123) Conforms to federal bridge formula 131,600 Colorado (54) Permit 85,000 2+ axles 97,000 4 axles 110,000 Delaware (17) Permit vehicle 120,000 Florida (125) 4 axles, 17-ft wheelbase, Map 1, truck cranes 88,000 4 axles, 22-ft wheelbase, Map 2, truck cranes 97,000 9 axles, 51-ft wheelbase, Map 3, truck cranes 125,000 7 axles, 65-ft wheelbase, Map 1, wreckers 140,000 7 axles, 61-ft wheelbase, Map 2, wreckers 140,000 8 axles, 75-ft wheelbase, Map 2, blanket permit 160,000 10 axles, 90-ft wheelbase, Map 1, blanket permit 162,000 11 axles, 100-ft wheelbase, Map 3, blanket permit 199,000 Idaho (58) Interstate routes 105,000 Yellow routes, 200,000 max. Orange routes, Green routes, Blue routes, Purple routes, Black routes, (continued on next page)

TABLE 57 (continued) State Configuration Load (lb) Illinois (9, 128) Tractor, semi-trailer 88,000 5 or more axles 100,000 6 or more axles 120,000 Combination, 2 axle semi-trailer 100,000 3 axle semi-trailer 120,000 Indiana (145) Extra heavy duty highway 264,000 Indiana (129, 146) Ocean-going container 95,000 Tractor-trailer-trailer 127,000 Tractor-trailer-trailer-trailer 127,400 Extra heavy duty highway 134,000 Extra heavy duty highway 264,000 Iowa (60, 147, 148) Annual permit 156,000 Tracked implement of husbandry 96,000 Alternative energy construction 256,000 Kansas (94) Special vehicle combination 110,000 Annual permit 120,000 Standard permit, 91-ft wheelbase 150,000 Special mobile equipment, 64-ft wheelbase 150,000 Kentucky (130) Self-propelled truck crane, 4 axles 92,000 5 axles 96,000 Self-propelled truck crane, 5 axles 115,000 6 axles 120,000 7 axles 160,000 Louisiana (131) Sealed containerized cargo 90,000 Bagged rice 95,000 Sugarcane, agronomic, or horticultural crops 100,000 Timber equipment 105,000 Minnesota (99) Pole-length pulpwood, 6-axle 82,000 Hauling livestock 88,000 Livestock 88,000 Paper products, 2-unit 99,000 Farm products, 6 axles 99,000 Sealed intermodal container 99,000 Canola hauling, 3-unit 105,500 Paper products, 3-unit 108,000 Construction equipment, boat hauler, farm machinery 145,000 Mobile cranes; construction equipment, machinery, and supplies; implements of husbandry; commercial boat hauling 155,000 Maine (63, 149) Pilot project, 3 axle tractor + 3 axle semi-trailer 108,900 6+ axles, multi-state permit 120,000 Pilot project, 8 axle combination 137,700 Maryland (150) Book permit 90,000 Massachusetts (151) Tractor-trailer 99,000 5+ axles, non-reducible 130,000 Michigan (84, 133) Raw forest products 90,000 Construction equipment 150,000

TABLE 57 (continued) State Configuration Load (lb) Montana (134, 152) Eureka Mt. to British Columbia 137,500 160,000 New Mexico (105) Interstate routes 86,400 Port of entry + 6 miles, reducible load OK 96,000 Annual permit 140,000 New York (153, 154) Type 4 (F5), 5 axles, 30-ft wheelbase 93,000 Type 1 (F1), 3 axles, 16-ft wheelbase 97,400 Divisible load 102,000 Type 1A (F1), 5 axles, 16-ft wheelbase 102,000 Type 7 (F2), 6 axles, 35.5-ft wheelbase 107,000 Type 9 (F2), 7 axles, 43-ft wheelbase 117,000 Type 6A (F5), 6 axles, 36.5-ft wheelbase 120,000 Type 6B (F5), 7 axles, 43-ft wheelbase 120,000 Mississippi (100) Harvest permit 84,000 Missouri (101) 5 axles 105,000 6 axles 120,000 7 axles 150,000 8+ axles 160,000 North Carolina (135) Annual permit 90,000 4 axles single vehicle 90,000 4 axles single vehicle, self-propelled off-highway construction equipment 90,000 5 axles single vehicle 94,500 6 axles single vehicle 108,000 5 axles combination vehicle 112,000 6 axles combination vehicle 120,000 7 axles single vehicle 122,000 7 axles vehicle combination 132,000 North Dakota (72) 4 axles, special mobile equipment 96,800 4 axles, self-propelled workover rigs 100,700 5 axles, special mobile equipment 106,800 5 axles, self-propelled workover rigs 111,100 6 axles, special mobile equipment 114,800 6+ axles, self-propelled workover rigs 114,800 Identification supplement, workover service rig 119,500 Identification supplement 150,000 Ohio (136) Toledo, Ohio to Delta, Ohio 154,000 Oklahoma (141) 5 axles 95,000 6 axles 115,000 Annual envelope permit 120,000 7 axles 135,000 8 axles, Standard Overweight Permit Trucks 155,000 9 axles, Standard Overweight Permit Trucks 172,000 10 axles, Standard Overweight Permit Trucks 189,000 11 axles, Standard Overweight Permit Trucks 195,000 14 axles, Standard Overweight Permit Trucks 202,000 13 axles, Standard Overweight Permit Trucks 209,000 12 axles, Standard Overweight Permit Trucks 211,000 (continued on next page)

40 State Configuration Load (lb) Oregon (74, 137) 7 axle, 78-ft wheelbase, Permit Weight Table 2 105,500 Non-divisible 200,000 11+ axles, 150-ft wheelbase, Permit Weight Table 3 228,000 15+ axles, 150-ft wheelbase, Permit Weight Table 4 304,000 Tennessee (109) Permit without evaluation of structures 200,000 Texas (76) Annual permit, overweight or oversize equipment 120,000 Permit by Port Authority 125,000 Victoria County Navigation District permits 140,000 Permit limit without evaluation of structures 200,000 Utah (77) Annual permit, non-divisible load 125,000 Annual permit, divisible load 129,000 6 axles, 10-ft width, 60-ft wheelbase 152,000 Utah (124) Non-divisible loads, 125,000 min Virginia (78, 138) Annual permit, non-interstate routes 84,000 4 axles, 61-t wheelbase 96,000 5 axles, 64-t wheelbase 102,500 6 axles, 64-ft wheelbase 108,500 7 axles, 64-ft wheelbase 115,000 Washington (79) Heavy haul industrial corridor 105,500 To/from Oroville railhead 139,994 West Virginia (80) Routine permit 90,000 Routine permit 110,000 Wisconsin (81, 142) Moving farm machinery, sealed loads for international trade 90,000 6 axles, 60-ft wheelbase 90,000 7 axles, 52-ft wheelbase 90,000 8 axles, 42-ft wheelbase 90,000 Among manufacturing plants along SH 31; raw forest or agricultural products 98,000 Annual permit, 2 + 2 axles, 18 ft interior spacing 115,000 Annual permit, 4 + 4 axles, 18 ft interior spacing 150,000 Pole, pulpwood or coal hauling 154,000 Within 11 miles of the Wisconsin−Michigan border 154,000 Wyoming (111) Self-issuing permit 117,000 Permit 150,000 TABLE 57 (continued) For ASR and LFR methods RF C A DA L I( )= − +1 (2) 1 2 where C = Load capacity, A1 = Load factor for dead load, D = Dead load, A2 = Load factor for live load, L = Live load, and I = Impact factor. For the LRFR method RF C DC DW PLL IM DC DW P LL )(= − γ − γ ± γ γ + (3) where C = Load capacity adjusted for deterioration and load path redundancy; gDC = Load factor for dead load of structural components; DC = Dead load of structural components; gDW = Load factor for load of wearing surface and utilities; DW = Load of wearing surface and utilities;

41 Thirty-four states use more than one basis, with 18 using all three bases. Several states retain LFR and ASR load ratings for existing structures, and apply LRFR to newly designed structures. Several states use ASR specifically for timber bridges. U.S.DOT policy requires states to report load ratings using the LRFR basis for structures designed or replaced after Octo- ber 1, 2010 (155). For other structures, load ratings may be reported using the LRFR or LFR basis. Load ratings for tim- ber bridges and masonry bridges may be reported using ASR basis. Details of the state responses in the survey on methods of load rating are listed in Table 21. Computational load rating uses computational methods of structural analysis. Methods of structural analysis include two-dimensional analysis using live load distribution factors and three-dimensional analysis using grillage models or finite- element models. Two-dimensional analysis, called beam line analysis, follows common design practice for bridges. Three- dimensional analysis methods are refined (better than two- dimensional) methods. All survey states use beam line analysis in load rating computations (Table 60). Twenty-four states use refined analysis methods for some load rating computations. Survey responses on the uses of refined analysis are listed in Table A24. gP = Load factor for other permanent loads; P = Other permanent loads; gLL = Load factor for live loads; LL = Live loads; and IM = Dynamic effect of live loads. Assigned Load Ratings Load ratings can be assigned to structures based on their design loads. Design calculations must correspond to struc- tures in service. Structures must be built as designs intended, must not be modified in ways that affect strength, and must not have deterioration that affects strength. FHWA sets limits on the use of assigned load ratings for reporting under NBIS (155). Structures must be designed by load factor design or load and resistance factor design methods, design loads must be HS20 or HL93 or greater, and design loads must produce load effects in structure members that are at least as great as states’ legal loads and states’ routine permit loads. Load Rating by Load Testing Load tests are used in structure load rating. There are two types of load tests: diagnostic load tests and proof load tests. Diagnostic load tests establish structure-specific live load dis- tribution factors and reveal the inherent extra load capacity owing to the unintended composite action of beams with decks and the participation of nonstructural elements in load paths. Proof load tests make direct demonstrations of load capacity. Proof load tests apply known live loads to struc- tures. Safe load capacity is set at a value less than the proof load. The difference between proof load and safe load pro- vides a margin of safety for traffic on the structure. Load Rating by Field Evaluation and Engineering Judgment Load rating by FE/EJ is the presumptive assignment of a safe load capacity when load rating by computation is not possible, usually because of a lack of as-built plans (156). AASHTO advises that if structures are in service and show no distress it is not necessary to post for restricted loadings (5). FE/EJ is suitable for structures that are already in service, and show no significant distress. STATES’ USE OF LOAD RATING METHODS All survey states use computational methods for load rating. Nineteen states use load tests, and 27 states use FE/EJ load rating (Table 58). Survey responses on methods of load rating are listed in Table A20. Load Rating by Computation Thirty-nine survey states use the LFR basis for computa- tional load rating, 29 use LRFR, and 27 use ASR (Table 59). TABLE 58 SUMMARY—METHODS OF LOAD RATING Method of Load Rating States Count Computational Load Rating 43 Load Test 19 FE/EJ 27 TABLE 59 SUMMARY—BASIS FOR LOAD RATING Basis for Load Rating States Count ASR 27 LFR 39 LRFR 29 TABLE 60 SUMMARY—METHODS OF STRUCTURAL ANALYSIS Method of Analysis States Count Beam Line 43 Refined 24

42 distribution in the structure; proof load tests are applied to reach load effects at the level of the operating rating (84). Missouri applies proof load tests to reinforced concrete bridges with unknown details for steel reinforcement. Missouri sets bridge load capacity at 75% of the proof load (161). Wisconsin does not use load test to determine load ratings (27). Survey responses on the use of load testing in load rating are listed in Table A26. Notes on States’ Use of Field Evaluation and Engineering Judgment in Load Rating For FE/EJ load ratings, Indiana advises load raters to assume that concrete beams have flexural steel reinforcement equal to 75% of balanced flexural reinforcement, if reinforcement is not otherwise known (19). Massachusetts does not allow FE/EJ load rating (157). Michigan cautions load raters that FE/EJ load ratings are appropriate only with a clear knowl- edge of expected traffic on the bridge (84). Minnesota defines Physical Inspection Ratings (PIR), a type of FE/EJ load rating (37). PIRs are assigned where design plans are not available, or effects of deterioration on load capacity cannot be modeled adequately. Minnesota requires safety inspection every 12 months or less for bridges with PIR load ratings. Minnesota excludes overweight permit loads from these bridges. New York State DOT uses FE/EJ as a temporary measure until further analysis is performed. A typical case would be damage resulting from impact. Texas sets FE/EJ operating ratings equal to HS20 if bridges have been carrying unrestricted traffic for many years and there are no signs of distress. For FE/EJ load ratings, Texas requires that span/depth ratios not exceed 20, that dimensions of beams and slabs be consistent with adequate cover for steel reinforcement, and that the general appearance of bridges be consistent with construction by a competent builder (39). Utah sets FE/EJ load ratings equal to Utah legal loads (34). Virginia sets FE/EJ operating ratings equal to the design load used at the time of bridge construction (25). Washington sets FE/EJ inventory ratings equal to the design truck at the time of bridge construction, provided that current values of NBI GCRs for superstructure and substructure are 5 or higher (159) (Table 62). Wisconsin requires inspections at six-month inter- vals for reinforced concrete bridges that have FE/EJ load ratings and were built before 1974 (27). Survey responses on the use of FE/EJ load rating are listed in Table A25. Weight Limits for Load Posting Weight limits for load posted structures may be set at operat- ing ratings, at inventory ratings, or at intermediate levels. AASHTO (5) provides a load posting equation for use with LRFR that yields intermediate levels that are proportional to structures’ rating factor. Refined methods of structural analysis are applied to com- plex bridges, to bridges that should not be analyzed using AASHTO live load distribution factors, and to other bridges as needed to evaluate overweight permit loads or to avoid load posting (Table 61). AASHTO recommends the use of refined analysis in place of beam line analysis when beam line analysis yields a low load rating (5). Notes on States’ Use of Refined Methods of Structural Analysis Colorado applies the same method for design analysis and for rating analysis to each bridge (16). In Louisiana, prior approval from the state bridge rating engineer is needed for the use of refined analysis (20). Massachusetts uses Virtis software for most load ratings (157), and STAAD (158) or GT-STRUDL (41) for refined analysis of arch bridges. Load rating analysis can be refined by the use of specialized live load distribution factors. Michigan DOT (84) publishes a list of live load distribution factors for sawn timber bridges, glued-laminated timber bridges, and bridges with steel grid decks. Minnesota (37) uses refined analysis for curved girder bridges, segmental concrete bridges, and cable-stayed bridges. Washington requires refined analysis for steel truss bridges (159). Washington uses two-dimensional models for each parallel truss, as well as three-dimensional models of entire, multi-truss bridges. Workload is a concern. Minnesota cautions load raters to consider the additional work for refined analysis in relation to the potential benefit (37). When West Virginia uses refined analysis in the design of new bridges, conversion factors are computed that relate results of refined analysis to results of beam line analysis (160). With conversion factors, West Vir- ginia can apply beam line analysis in subsequent evaluations of bridges. Survey responses on the use of refined methods of analysis are listed in Table A24. Notes on States’ Use of Load Testing for Load Rating Michigan uses both diagnostic load tests and proof load tests. Diagnostic load tests are used to obtain accurate live load TABLE 61 SUMMARY—USE OF REFINED ANALYSIS Reason for Refined Analysis States Count Avoid Posting 18 Complex Bridge 14 Both 6 Not Used 17

43 redundancy. Five states post at the inventory rating, and four use AASHTO’s posting equation (Eq. 4). Delaware posts at four levels in the range of the inventory rating to the operating rating (17) (Table 64). Structures in poor condition are posted at the inventory rating, while struc- tures in good condition with load path redundancy are posted at the operating level. Detour length, ADTT, and enforce- ment of weight limits affect posting level. Massachusetts posts at inventory rating, but will not post at all if a bridge has an inventory rating that is not more than 5% below the weights of Massachusetts posting trucks (157). Missouri posts for load at the operating rating and at inter- mediates levels. Posting level depends on the method of load rating, fatigue vulnerability, and bridge location (Table 65) (161). Montana DOT posts bridges that have an operating rating less than 40 tons for an AASHTO Type 3-3 vehicle (21). Montana posts bridges at their inventory ratings. New York posts at the operating rating for bridges in good condition that are load path redundant (22) (Table 66). Bridges Safe Posting Load W RF[ ]= −0.7 0.3 (4) where W is the gross weight of a rating vehicle, and RF is the rating factor for the same vehicle. Twenty-two survey states post structures at the operating rating (Table 63). Twelve states post at intermediate levels between inventory rating and operating rating. Intermediate levels are set in relation to structure condition and load path TABLE 62 WASHINGTON STATE DOT GUIDANCE ON LOAD RATING BY FE/EJ Inventory Rating Equal to Design Truck at Time of Construction Operating Rating Load Posting None if general condition rating for superstructure and substructure Post for load if general condition rating for superstructure or substructure Overweight Permit Loads Overweight permit loads excluded if general condition rating for superstructure or substructure Source: Washington State DOT (159). TABLE 63 SUMMARY—LOAD POSTING LEVEL Posting Level States Count Inventory Rating 5 Operating Rating 22 LRFR Posting Equation 4 Other/Intermediate 12 TABLE 64 DELAWARE LOAD POSTING LEVELS NBI General Condition (deck, super or sub) Load Path Redundant Detour (km) Fatigue Sensitive Details ADTT Enforcement Level Posting Level Y >16.1 N Y 40 >40 Vigorous 16 N Y 40 >40 Moderate Minimal N <4 = Operating Rating. = Inventory Rating. Source: Bridge Design Manual (17).

44 Structures Rating Method Posting Level Bridges, Generally ASR Using allowable stress = 0.68Fy LFR 0.86 Bridges in commercial zones Load path redundant & ADT < 1000 & no fatigue sensitive details Load path redundant & ADT < 200 Source: Load Rating of Non-State System Bridges (161). Fy = Material yield stress. = Operating Rating. TABLE 65 MISSOURI LOAD POSTING LEVEL Bridge Type and Characteristics Primary Member Condition Rating1 Safe Load Capacity Posting for steel primary members are load path non-redundant, or for primary members with extensive section loss 3 4 Posting for primary members that are load path redundant, or for floor system members, or for concrete beams or slabs 3 4 Posting for load path redundant members and floor system with known excess capacity, or for compression chords of trusses with adequate lateral support no signs of lateral movement Source: Load Rating Posting Guidelines for State-Owned Highway Bridges (22). 1In New York State’s condition rating scale, rating “3” indicates severe deterioration that may affect strength. = Operating Rating. TABLE 66 NEW YORK SAFE LOAD CAPACITY DETERMINATION GUIDELINES are posted below operating rating if primary members are in poor condition or bridges are not load path redundant. New York excludes permit loads on bridges that have a pri- mary member with a condition rating below 4 or structural decks with a condition rating below 2. In New York’s con- dition rating scale, ratings below 4 indicate extensive, seri- ous deterioration. Oklahoma posts its on-system bridges when operating ratings are below 23 tons for an AASHTO H truck, below 36 tons for an AASHTO HS truck, or below 45 tons for an AASHTO Type 3-3 combination vehicle (33). Texas’ level for posting depends on structure condition, load path redundancy, and traffic volume. Texas publishes guidance for posting levels for structures on the state system and for structures not on the state system (39) (Tables 67 and 68). Virginia posts concrete bridges at operating rating, and posts steel bridges at the average of inventory rating and oper- ating rating (25). Survey responses on level for load posting are in Tables A22 and A23. Load Rating of Decks and Substructures Load rating computations evaluate structure components that can control load capacity. These always include superstruc- ture components and, less often, deck slabs and substructure components. AASHTO (5) notes that reinforced concrete deck slabs supported on stringers usually do not need to be evaluated for load capacity if slabs are performing satisfac- torily. Timber decks may control load ratings, especially if decks show excessive deflection under load. Substructures, similar to deck slabs, usually do not need to be evaluated for load capacity. Substructures are rated for load capacity if substructure condition is poor, if substruc- tures have distress that affects strength, or if substructures are essential to load paths. Twenty-one survey states evaluate the load capacity of decks. States evaluate load capacity of decks in poor con dition. States identify timber decks and metal decks particularly for load rating (Table 69). Twenty-seven survey states evaluate

45 TABLE 67 TEXAS LOAD POSTING LEVEL, ON-SYSTEM STRUCTURES Load Rating General Condition Ratings Inspection Interval, mos Load Posting IR HS20 — 24 None required OR HS20 Item 58 4 Item 59 5 Item 60 5 or Item 62 5 24 None required HS10 OR < HS20 Item 58 4 Item 59 5 Item 60 5 or Item 62 5 24 Post at operating level HS10 OR < HS20 Item 58 < 4 or Item 59 < 5 or Item 60 < 5 or Item 62 < 5 24 Post at inventory level IR HS3 and OR < HS10 — 24 Post at inventory level IR < HS3 and OR HS3 Bridge programmed for rehabilitation or replacement 61 Post at operating level or close bridge IR < HS3 and OR HS3 Bridge not programmed for rehabilitation or replacement — Close bridge OR < HS3 — — Close bridge Source: Bridge Inspection Manual (39). IR = Inventory rating. OR = Operating rating. Item 58 = Deck general condition rating. Item 59 = Superstructure general condition rating. Item 60 = Substructure general condition rating. Item 62 = Culvert general condition rating. 1If bridge is not rehabilitated or replaced within 24 months the bridge shall be closed. the load capacity of substructures. Substructures in poor con- dition, timber or steel bents, and substructures that, if failed, could cause bridge collapse are rated for load (Table 70). Notes on States’ Practices for Load Rating of Structural Decks Colorado identifies software packages for the load rating of decks (16). Florida load rates deck slabs in poor condition (18). For deck panel systems, poor condition entails load rating of the decks, plus modification of live load distribution factors for girders. Live load distribution factors are evaluated as if deck panels are simple spans. Indiana load rates deck slabs in poor condition, and instructs load raters to use field-determined sacrificial wear in the top surface of slabs for the evaluation of load capacity (19). Indiana rates timber decks on truss bridges. Michigan evaluates load capacity of decks in poor condition and decks of older bridges originally designed for H15 loading (84).

46 TABLE 68 TEXAS LOAD POSTING LEVEL, OFF-SYSTEM STRUCTURES Load Rating General Condition Ratings Inspection Interval, mos Load Posting IR HS20 — 24 None required OR HS20 Item 58 5 Item 59 6 Item 60 6 or Item 62 6 24 None required HS10 Item 58 5 Item 59 6 Item 60 6 or Item 62 6 24 Post at operating level HS10 Item 58 < 5 or Item 59 < 6 or Item 60 < 6 or Item 62 < 6 24 Post at inventory level IR HS3 and OR < HS10 — 24 Post at inventory level IR < HS3 and OR HS3 Bridge programmed for rehabilitation or replacement 61 Post at operating level or close bridge IR < HS3 and OR HS3 Bridge not programmed for rehabilitation or replacement — Close bridge OR < HS3 — — Close bridge Source: Bridge Inspection Manual (39). IR = Inventory rating. OR = Operating rating. Item 58 = Deck general condition rating. Item 59 = Superstructure general condition rating. Item 60 = Substructure general condition rating. Item 62 = Culvert general condition rating. 1If bridge is not rehabilitated or replaced within 24 months the bridge shall be closed. < < TABLE 69 SUMMARY—LOAD RATING OF DECKS Load Rating for Deck States Count Reason to Load Rate Decks States Count Yes 21 Deck Condition 6 Deck Material 4 Other 3 TABLE 70 SUMMARY—LOAD RATING OF SUBSTRUCTURES Substructure Load Rating for States Count Reason to Load Rate Substructure States Count Yes 27 Substructure Condition 11 Substructure Material 5 Other 10

47 Table 71 lists axle counts, wheelbase, and GVW for AASHTO legal load rating vehicles and for AASHTO HS20 design vehicles. Table 71 lists the ratio of GVW for rating vehicles to the limit on GVW obtained from the federal bridge gross weight formula (see Eq. 1). GVW GVWW=Ratio (5) where GVW is the gross weight of the rating vehicle, and W is the limit from the federal bridge gross weight formula for the same rating vehicle. Twenty-five survey states use AASHTO’s HS20 design vehicle in load rating (Table 72). Twenty-three states use AASHTO vehicles Type 3, Type 3S2, and Type 3-3. At the time of the survey in 2013, nine states were using one or more special hauling vehicles, SU4 to SU7. Thirty-two states use state-specific rating vehicles. Basic information on state rating vehicles is summarized in Table 73. Load rating vehicles used by states have GVW from 23,900 lb to 404,000 lb. GVW ratios for rating vehicles range from 1.00 to 2.93. Most of the heavy rating vehicles in Table 73 represent overweight permit vehicles. State policies on load rating require evaluation of the load capacity of bridges and culverts for these vehicles. Posting vehicles, the rating vehicles used in the evalua- tion of weight limits for load posted structures are a subset of load rating vehicles. AASHTO recommends the use of Type 3, Type 3S2, and Type 3-3 vehicles together with one special hauling vehicle in evaluation of posted structures (5). A sum- mary of state posting vehicles is shown in Table 74. Posting vehicles range in weight from 33,600 lb to 164,000 lb. GVW ratios range from 1.00 to 1.44. A detailed list of states’ posting vehicles appears in Table B6. OVERWEIGHT RATING VEHICLES Evaluation of a structures’ load capacity for overweight per- mit loads is, like load posting, an application of computational load rating. Evaluation for permit loads uses a set of over- weight rating vehicles; configurations of axle weights, counts, and spacings that are similar to actual overweight vehicles. The axle weights and spacings of actual vehicles are used in the evaluation of load capacity for special overweight permit vehicles. States’ overweight rating vehicles are summarized in Table 75. A detailed list of states’ overweight rating vehicles can be found in Table B7. Both tables include all overweight vehicles found in the state DOT publications reviewed in the preparation of this synthesis report. Some of the overweight vehicles listed in these tables are routine overweight permit vehicles and some are single-trip overweight permit vehicles. Most permit rating vehicles have GVW greater than 80,000 lb, Minnesota evaluates load capacity of decks in poor condition and evaluates decks for overweight permit loads (37). Nevada evaluates the load capacity of decks in poor con- dition (31). New Mexico routinely includes timber decks in load rating computations (46) and includes concrete deck slabs and metal decks in load rating if their condition is poor. New York evaluates the load capacity of timber and metal decks (22). Washington evaluates load capacity of bridge decks that have NBI GCR below 5 (159). Wisconsin rates bridge decks in poor condition (27). Virginia load rates decks if the deck span between girders is unusually large (25). Survey responses on load rating of decks are listed in Table A27. Notes on States’ Practices for Load Rating of Substructures Arizona rates substructure in poor condition (15). Delaware’s policy for most bridges is to rate superstructure components only (17). Delaware will rate decks or substructures if their condition is poor. Florida directs load raters to consider sub- structures in the context of load rating obtained for super- structures (18). Evaluation of load capacity is not needed for substructures that are judged to have load capacity at least as great as that of the superstructure. Indiana directs load raters to evaluate substructures that have GCR of less than 4 (19). Massachusetts rates steel, timber, and pile bent substructures, and other substructures if their condition is poor (157). Minnesota rates substructures for overweight permit loads as needed and rates substructures that are in poor condition (37). Nevada evaluates the load capacity of reinforced con- crete pier caps that have a GCR below 6 (31). New York evaluates load capacity of timber and metal piers (22). Utah evaluates the load capacity of steel or timber bents, and any substructure components with a GCR below 5 (34). Virginia evaluates load capacity of substructures in poor condition, substructures that have settled, and substructures that have collision damage (25). Wisconsin rates substructures compo- nents in poor condition (27). Survey responses on load rating substructures appear in Table A28. LOAD RATING VEHICLES Load rating computations use load rating vehicles; configura- tions of axle loads, axle counts, and axle spacings that pro- duce stresses in structures similar to stress under actual traffic. Rating vehicles are defined by AASHTO (5) and by states. Rating vehicles come in three classes: (1) design load vehicles, (2) legal load vehicles, and (3) overweight load vehicles. Load postings are determined by load rating using a subset of rating vehicles. In many states, this is the set of rating vehicles for legal loads.

48 tures can reduce the load capacity of components and must be recognized in the evaluation of load posting. For LRFR, AASHTO provides a condition factor, jc, as one way to include deterioration in load rating computations. Condition factor, jc, is related approximately to NBI GCRs. The factor is lower for lower condition ratings. Load rating computations can include explicit evaluations of the remaining strength of structure components. Remain- ing strength of components may be based on field-measured (remaining) dimensions of components or on tests of material coupons collected from structures. Forty-one survey states use field-measured dimensions to evaluate the remaining sections of structure components (Table 76). Fifteen states use material tests to obtain material strengths. Eighteen states use the AASHTO condition factor. Notes on States’ Use of Structure Condition in Load Rating California uses field measurement for deteriorated steel members, and reduced material stresses for deteriorated tim- with one as great as 480,000 lb. States’ permit vehicles have GVW ratios greater than 1.0 and as great as 2.93. CONDITION AND DETERIORATION IN LOAD RATING COMPUTATIONS Background Load ratings and load postings are based on existing con- ditions of structures. Deterioration in components of struc- Vehicle Wheelbase, ft GVW, kip GVW Ratio Rating Vehicle Type 3 19 50 1.00 Type 3S2 41 72 0.98 Type 3-3 54 80 0.93 SU4 18 54 1.00 SU5 22 62 1.00 SU6 26 69.5 1.00 SU7 30 77.5 1.00 Notional Load 30 80 0.96 HS20 28 72 1.26 HS20 Long 44 72 1.04 16k 17k 17k 15’ 4’ 10k 15.5k 15.5k 15.5k 15.5k 11’ 22’4’ 4’ 12k 12k 12k 16k 14k 14k 15’ 15’ 16’4’ 4’ 12k 8k 17k 17k 10’ 4’ 4’ 12k 8k 8k 17k 17k 10’ 4’ 4’ 4’ 11.5k 8k 8k 8k17k 17k 10’ 4’ 4’4’ 4’ 11.5k 8k 8k 8k 8k17k 17k 10’ 4’ 4’ 4’4’ 4’ 6k 8k 8k 17k 17k 8k 8k 8k 6’ 4’ 4’4’ 4’ 4’ 4’ 8k 32k 32k 14’ 14’ 8k 32k 32k 14’ 30’ TABLE 71 AASHTO LOAD RATING VEHICLES TABLE 72 SUMMARY—STATES’ USE OF RATING VEHICLES Rating Vehicle States Count HS20 25 Type 3, Type 3S2, Type 3-3 23 SHV (SU4 to SU7) 9 State Legal Load 32 SHV = special hauling vehicle.

TABLE 73 SUMMARY—STATE RATING VEHICLES State/Org. GVW, k GVW Ratio State/Org. GVW, k GVW Ratio Min. Max. Min. Max. Min. Max. Min. Max. AASHTO 50 80 0.93 1.26 Mississippi 72 80 1.00 1.04 Alaska 50 80 0.93 1.04 Missouri 40 92 0.98 1.26 Arizona 72 72 1.04 1.04 Montana 50 138 0.93 1.04 California 122 404 2.18 2.93 Nebraska 50 86 1.00 1.01 Colorado 48 192 0.98 1.81 New Hampshire 33.4 73 0.88 1.27 Delaware 40 80 0.81 1.44 New Mexico 33.6 86.4 0.76 1.26 Florida 34 120 0.89 2.11 New York 50 80 0.93 1.00 Georgia 50 80 0.93 1.04 North Carolina 50 80 0.93 1.04 Hawaii 54 80 0.93 1.00 North Dakota 50 80 0.93 1.04 Idaho 80 129 1.00 1.00 Ohio 30 80 0.75 1.00 Illinois 80 80 1.00 1.00 Oklahoma 50 90 0.93 1.05 Indiana 23.9 480 0.65 2.12 Oregon 50 258 0.93 1.60 Iowa 54.5 96 1.00 1.00 South Dakota 50 80 0.93 1.04 Kansas 50 80 0.93 1.04 Tennessee 50 80 0.93 1.04 Kentucky 72 72 1.04 1.04 Texas 72 80 1.00 1.04 Louisiana 40 88 0.91 2.22 Utah 96 132 0.98 1.10 Maine 34 100 1.00 1.00 Virginia 54 115 1.00 1.19 Maryland 72 80 1.00 1.04 Washington 50 207 0.93 1.77 Massachusetts 40 72 0.98 1.26 West Virginia 50 80 0.93 1.04 Michigan 33.4 164 0.93 1.40 Wisconsin 52 190 0.93 1.86 Minnesota 48 80 0.97 1.00 Wyoming 50 80 0.93 1.04 TABLE 74 SUMMARY—STATE POSTING VEHICLES State GVW, k GVW Ratio State GVW, k GVW Ratio Min. Max. Min. Max. Min. Max. Min. Max. Alaska 38 50 1.00 1.03 Minnesota 48 80 0.97 1.00 Colorado 48 85 0.98 1.12 Missouri 40 92 0.83 1.23 Delaware 40 80 0.81 1.44 Nebraska 50 86 1.00 1.01 Florida 70 80 0.89 1.30 New Mexico 33.6 86.4 0.76 1.05 Iowa 90 96 1.00 1.00 Virginia 54 80 1.00 1.00 Louisiana 41 88 0.91 1.16 Wisconsin 54 98 1.00 1.16 Michigan 33.4 164 0.86 1.40 State GVW, k GVW Ratio State GVW, k GVW Ratio Min. Max. Min. Max. Min. Max. Min. Max. California 122 404 1.94 2.93 Nevada 314 314 2.55 2.55 Colorado 100 192 1.75 1.81 New Hampshire 69 99 1.27 1.31 Florida 55 199 1.24 2.11 New York 27 120 0.46 2.03 Indiana 89.6 480 1.16 2.12 Oklahoma 93 211 1.11 1.50 Iowa 90 156 1.06 1.63 Oregon 43 304 0.93 1.73 Louisiana 133 260 1.47 2.22 Utah 96 132 0.98 1.10 Maryland 52 150 1.40 1.52 Virginia 90 115 1.18 1.19 Michigan 120 283 2.06 2.93 Washington 66 207 1.44 1.77 Minnesota 104 256 1.20 1.68 Wisconsin 190 190 1.86 1.86 TABLE 75 SUMMARY—STATE OVERWEIGHT RATING VEHICLES

50 the TRB database on research in progress (164). Research projects included the use of field-measured responses of bridges to calibrate refined models for structural analysis and to obtain structure-specific distribution factors for live load, use of WIM data to characterize traffic on rural roads, evalu- ation of load effects of special vehicles such as implements of husbandry, development of load rating methods for com- plex bridges such as tied arches and segmental box girder bridges, and evaluation of multiple presence factors. Notes on States’ Research Related to Load Posting From Survey Alaska is applying structural health monitoring as part of the load rating for its Chulitna River Bridge. Delaware is study- ing effective widths of concrete slab bridges for load rating. Florida has developed a short special hauling vehicle for use in load rating (18). Iowa, Illinois, and Wisconsin are partici- pating in a pooled fund study of load rating methods adapted for implements of husbandry (165). Louisiana is developing rating vehicles using WIM data. Michigan has examined the probability of side-by-side occurrences of vehicles on bridges (166). Missouri is study- ing the relation of fill heights to load ratings of box culverts. New Mexico is studying methods for load rating of bridges that lack as-built plans. New York has evaluated LRFR methods for load rating and posting (167). North Dakota is re-evaluating its existing allowance of 10% greater loading for agricultural hauling during harvest season. Oregon is using WIM data to generate site-specific live load factors for use in LRFR. Virginia used load testing of a continuous slab bridge to validate the load ratings (168). Wisconsin is studying the effects of oversize, overweight vehicles on complex bridges, and has studied the effects of overweight permit vehicle loads on bridges (169). Survey responses on research activities are listed in Tables A31–A34. From TRB—Research in Progress The University Transportation Center at the University of Alabama funded a study on the use of field data acquired during bridge WIM tests for re-evaluation of bridge load ratings and load postings (170). Florida DOT is funding work by Florida State University to evaluate safe load capacity of prestressed segmental concrete box beam bridges carrying overweight permit vehicles (171). Iowa DOT funded work at the Iowa State University to determine the safe load capacity of bridges carrying farm wagons, carts, applicators, and tractors (172). The study included load tests at ten bridges in the state. Kansas DOT is ber components. Florida prefers to use field measurement for deterioration in components, but allows use of the condition factor jc if measurements are not available (18). Kansas uses the health index of superstructure elements as a condition factor. If the load rating computation indicates a need for posting, explicit evaluations with field measurements are made. Massachusetts requires field measures to quantify deterioration and applies field material sampling and testing if material properties are unknown (157). Maryland includes section losses in load ratings when loses are significant. Michigan includes section losses when loses are greater than 25% of the original values of section properties (84). Nebraska uses field measurements for structures with low NBI GCRs (162). Nevada uses reduced material properties in load computations for components with deterioration, and applies field measurements to define section properties of components (31). New Mexico requires field measurements of structure components for load rating of structurally defi- cient structures (46). New York recognizes deterioration by a reduction to structure operating rating (22). Oregon applies both field measurements for deteriorated sec- tions and a condition factor, jc (163). Tennessee reduces section properties and material stress limits for known deterioration. Virginia defines its own condition factor, jc, and relates the factor to NBI GCRs (25). Washington uses field measurements of remaining sections when available. When deterioration is described in general terms only, Washington uses lower val- ues of resistance factors, f in load rating. Resistance factors are reduced by 0.10 for components with element-level condition equal to 3 (fair condition) and reduced by 0.20 for components with element-level condition equal to 4 (poor condition) (26). Wisconsin uses field measurement of sections and makes further reduction to capacity if deterioration includes fea- tures that could be stress concentrations (27). RESEARCH RELATED TO LOAD POSTING Background Information on current research related to load posting was collected from the survey distributed to U.S. states and from TABLE 76 SUMMARY—USE OF CONDITION OF STRUCTURE COMPONENTS IN LOAD POSTING Use of Condition Data States Count Condition Factor 18 Section Properties from Field Measurement 41 Material Coupons 15

51 products from farms, forests, or mines; and some vehicles owned by public utilities or state or local governments. Vehicles that exceed limits on legal loads routinely travel on U.S. highways, including interstate highways, using over- weight permits issued by states. Most survey states issue overweight, multi-trip permits for vehicles with GVW equal to or greater than 100,000 lb. All survey states use computational methods for load rating. All survey states apply approximate structural analysis using live load distribution factors for load rating. Twenty- four survey states also use refined, three-dimensional meth- ods for structural analysis. Thirty-nine survey states use the LFR basis for computational load rating, 29 use LRFR, and 27 use ASR. Nineteen survey states use load tests. Less than 0.01% of U.S. bridges and culverts have load ratings determined by load tests. Twenty-seven survey states use FE/EJ load rating. Two percent of U.S. bridges and culverts have load ratings determined by FE/EJ. Twenty-two survey states use operating load ratings to set weight limits at posted structures. Twelve survey states set weight limits between inventory and operating load ratings. The particular selection of weight limit at posted structures can depend on GCRs, load path redundancy, detour length, and average daily traffic. Most survey states include bridge decks and substructures in load rating computations if their condition is poor. Vehicles used in load rating computations determine numer- ical specifications of counts, spacings, and weights of axles. AASHTO’s load rating vehicles, shown in the Manual for Bridge Evaluation (5), are used by 33 survey states. Thirty- two survey states define additional rating vehicles for legal loads. Nineteen survey states define overweight vehicles for load rating. Forty-one survey states use field-measured dimensions of components to account for deterioration when performing load rating computations. Eighteen survey states use AASHTO’s condition factor, jc. Current research related to load posting includes use of WIM data to characterize truck loads and to evaluate live load distribution factors and multiple presence factors, calibration of refined models for structural analysis, development of load rating methods for complex bridges, and evaluation of effects of special vehicles on bridges. funding work by the University of Kansas to evaluate load capacity of single-cell box structures beneath shallow low fill (173). The study includes load tests at two structures and three-dimensional finite-element analysis. Nebraska Department of Roads funded a study by the Uni- versity of Nebraska for load rating of two tied-arch bridges using three-dimensional finite-element models (174). Nebraska Department of Roads is also funding work by the University of Nebraska to determine appropriate truck loads and multiple presence factors for rural, county-owned bridges (175). The study is using WIM data to quantify truck loads. New York State DOT funded work by the City College of New York to develop load factors for use in LRFR load rating and load posting (176). Load factors are calibrated to data on truck weights collected at New York DOT’s WIM sites. Ohio DOT is funding a study by Youngstown State Univer- sity in the use of field-measured accelerations under load to track deterioration in prestressed concrete box beam bridges (177). Field accelerations are used with finite-element mod- els to quantify deterioration and to yield bridge load ratings. Vermont DOT is funding work by the University of Ver- mont to compare load effects of the AASHTO HL93 loading with load effects of actual truck traffic (178). Quantitative information on truck traffic is developed from data collected at WIM sites in Vermont. U.S.DOT funded work by the University of Delaware to establish the effects of deterioration in reinforced concrete bridge decks on load path redundancy in multi-beam steel bridges (179). The study developed a procedure to identify the bridges that have the greatest need for rehabilitation or replacement. SUMMARY Legal loads for motor vehicles on highways are established in state law. USC Title 23 sets limits on loads for interstate highways. Federal regulation sets limits for single-axle load, tandem-axle load, and GVW for interstate highways. Most states set their legal loads equal to the limits in federal regula- tion; however, some set higher limits for one or more among single-axle loads (13 states), tandem-axle loads (17 states), or GVW (18 states). State laws provide exemptions from load limits for some vehicles. Exemptions are tied to vehicle use, to the commod- ity being transported, or to the vehicle owner. States exempt some farm equipment and construction equipment; some raw