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APPENDIX H GLOSSARY OF TERMS With Relevance to NCHRP Project 20-34 A automatic vehicle identity cation (A VI) - AVI is one technology from the family of transportation technologies known as Intelligent Transportation Systems (ITS). AV} systems transmit data from a moving vehicle to data gathering centers via a communications device at the roadside. Agencies investing in AV! systems will use it to better monitor the types of trucks using a state's highways, whether specially permitted vehicles are traveling within permit bounds, and to ensure carriers are complying with all legal limits. AV} is also being used in some states along the I-75 corridor to allow legally registered and permitted carriers to bYnass weigh stations between designated points on the highway. ~_' . - ~ r ~o- _ =, ~ axle - (~) the common axis of rotation of one or more wheels whether power-driven or freely rotating, and whether in one or more segments, and regardless of the number of wheels carried there-on; (2) a shaft on which or with which two or more wheels on a vehicle revolve; (3) the pin or shaft with which a wheel or pair of wheels revolves. Axles have federally designated weight limits, according the overall size and gross vehicle weight of the truck. apache group - (~) an assemblage of two or more consecutive axles considered together in determining their combined load effect on a bridge or pavement structure; (2) two or more consecutive axles considered together in determining their combined load effect on a bridge or pavement structure. aucie load - the weight carried by one axle of a vehicle. Annie spacing - the distance between two consecutive axles of a truck or combination, usually measured from Be point of ground contact of one tire to the same point on the other tire or from a point on an axle hub to the same point on the other axle hub. article weigh f - the weight transmitted to the surface by one axle or a combination of axles in a tandem assembly. B base course- the layer or layers of specified or selected material of designed thickness placed on a subbase or a subgrade to support a surface course. Glossary
bills of lading - Bills of lading, and other carrier documentation, specify the commodity, weight of the load, and provide other details about the transaction between shipper and receiver. Bills of lading and other documentation can be used by motor carrier enforcement officials to examine systematic violations of weight laws. (See Relevant Evidence) bingo stamp - A bingo stamp is a stamp purchased by a carrier for all vehicles in its fleet that is expected to operate within a particular state jurisdiction within that year. These identification stamps are proof that the carrier has obtained the appropriate operating authority for that vehicle. These stamps must be affixed to a Form D or D-1 Cabcard and must be displayed in the cab of each vehicle. A stamp requires a fee that ranges from $ 1 to $ ~ 1, depending on the state. bridge formula - a standard to control the spacing of truck axles on vehicles that use highway bridges. bridge formula limit - the Federal law states that any group of two or more consecutive axles may not exceed the weight as computed by the Bridge Formula even though the single axle, tandem axles, and gross weights are within legal requirements. bypass - routes (usually state roads) which allow a truck to go around weigh stations, which are typically located on the interstate system, and to avoid safety and weight inspections. bus - a motor vehicle designed primarily for the transportation of persons rather than property and having a passenger-carrying capacity of 10 or more persons, other than a taxicab constructed and designed for transporting persons for commercial purposes. C cargo - the items of freight to be moved; including items placed on or in a vehicle, towed by a vehicle, or a vehicle itself. combi7'ation - (1) a truck or tractor coupled to one or more trailers (including semitrailers); (2) a power unit used in combination wad trailers and semitrailers. commercial vehicle - Any vehicle that has a GVW or GCW of 10,001 pounds or more; or, the vehicle is designed to transport more than 1 5 passengers including the driver; or, a vehicle used for transporting hazardous materials requiring placarding. compliance reviews - Compliance reviews are conducted on carriers with unsatisfactory safety review ratings (see "Safety Reviews"~. These reviews identify safety-related violations, levy fines, and require correction of all problems within 45 days. If a carrier has not qualified for a conditional or satisfactory safety review rating by the end of the 45 day period, the carrier is prohibited from transporting hazardous materials or passengers. connecting mechanism - an arrangement of parts interconnecting two or more consecutive axles to the frame of a vehicle in such a manner as to equalize the load between axles. Glossary 2
cost-effectiver~ess - the situation that exists when the benefits exceed the costs for a given treatment, strategy, or improvement or when the benefit cost ratio is greater chart one. credentials - term used to describe all paperwork a truck driver is required to have processed arid have copies available for inspection throughout the duration of a truck trip. D dynamic weight - the weight of a vehicle or an individual axle as measured while the vehicle is in motion. EESA.! - equivalent single axle load. equivalent Cole load (EEL) - the damage per pass to a pavement caused by a specific axle load relative to the damage per pass of a standard 1 8,000 point axle load moving on the same pavement. equivalent single axle loads fESALs) - the unit of measurement equating the amount of pavement consumption caused by an axle or group of axles, based on the loaded weight of the axle group, to the consumption of a single axle weighing 18,000 pounds. The summation ESALs is used to combine mixed traffic to design traffic for the design penod. Excess ESALs - excess ESALs equal the sum of the total ESALs attributable to the illegal portion of Me individual single or tandem axle group. F f nes - are payments levied to deter potential and repeat offenders from traveling illegally, and to recover administrative, court, and jail costs incurred in processing citations. Theoretically, the amounts of the fine levied are related to the amount of damage imposed on the road by an illegally overweight vehicle. Fine revenues are distributed differently In all states. Eked weigh station - A weigh station is a facility, usually located on the interstate highway system, at which trucks can undergo weight and safety inspections. There are weigh scales and often (but not always) a scale house to house inspectors between trucks. flexible pavement - a pavement structure which maintains intimate contact with and distributes loads to the subgrade and depends on aggregate interlock, particle friction, and cohesion for stability. friction' number (skid number) - the number that is used to report the results of pavement friction tests conducted in accordance with ASTM Standard E274. fuel tax - All states have some form of tax on diesel fuel or a substitute fee or usage type of tax which replaces the revenues that the diesel fuel tax would otherwise generate. Motor fuel taxes are sometimes called "second structure" taxes, because they were the second major source of highway Glossary
revenues to be introduced. In most states, they are the largest source of motor carrier-related state tax revenue. Intrastate vehicles, by the nature of their operations, pay their fuel taxes on fuel that is both purchased and consumed in the same state. However, large trucks can travel long distances without refueling, so it is easy for interstate operators to cross entire states without paying fuel taxes at the pump. Because of this, most states have instituted a procedure for motor carrier fuel use taxes in which a truck operator is responsible for reporting state mileage traveled, calculating fuel consumed within the states, and paying the taxes calculated as being due on the fuel consumed in that state. Originally, each state had its own fuel tax reporting requirements. However, the International Fuel Tax Agreement (IFTA) and the Regional Fuel Tax (RFTA) were formed about 12 years ago to encourage uniform administration of the Mel tax laws, and to establish a base state arrangement for collecting and administering fuel taxes. full frailer - a truck trailer with wheels on the front and rear (as opposed to a semitrailer in which the front rests on the rear of the tractor). G gross combined weigh f (GC~ - The weight of the power unit and trailer and the maximum payload. gross vehicle weigh! (GV~ - The weight of the vehicle plus the weight of any load thereon. gross weigh! - the weight of a vehicle and/or combination of vehicles plus the weight of arty load thereon. H heavy truck - a term used to describe a Suck weighing in excess of 80,000 pounds of gross vehicle weight. Heary Vehicle Use Taut (HVU~ - The Heavy Vehicle Use Tax is a federal tax levied on all common and contract carriers. It is an annual tax on carriers with registered gross vehicle weight, or gross combination weights, over 55,000 pounds. This tax is intended to cover pavement darnage caused by heavy vehicles. Before a carrier can be registered, the owner must show that it has properly paid this federal tax. height - the total vehicle dimension of a vehicle above the ground surface including any load and Toad-holding device thereon. HELP - Heavy Vehicle Electronic License Plate Project--a project that (among other achievements) set early standards for weigh-in-motion equipment. Glossary 4
International Registration Plan CARP) - an agreement between states for prorating fees between jurisdictions based on percentage of miles traveled by a fleet in each jurisdiction. inspection levels - This refers to the five levels of inspection carried out as part of the Motor Carrier Safety Assistance Program (MCSAP). These levels are: Level 1, the North American Standard, is the most thorough inspection. Conducted at the roadside, it covers both the driver and the vehicle, and includes inspecting underneath the vehicle. Level 2 is the same as Level 1, except that it does not include inspecting underneath a vehicle, while Level 3 covers only the driver. Level 4 is a special inspection of a particular item generally done in support of a study or to check a suspected trend. Level 5 is the same as Level 1, except that it is conducted at the terminal and does not include inspection of the driver. International Fuel Tax Agreement (IFTA) - This agreement was established about twelve years ago to encourage uniform administration of the motor fuel taxation laws, and to establish a base state arrangement for collecting and administering fuel taxes. Licensing with the base state satisfied a carrier's fuel tax licensing obligations to all members and the base state distributes payments and collects refunds for its carriers. The base state issues an external feel tax decal for each fleet vehicle, and these decals are reissued annually. The base state may levy a fee for the decal on its own carriers, but may not collect fees imposed by other states. The IFTA covers the same class of vehicles as does IRP, but differs in that reporting is by fleet, rather than by individual vehicle. As is the case with IRP, a vehicle which needs to travel in a state for which its fleet is not apportioned trader IFTA must obtain a temporary fuel tax permit for that state. Internatio,2al Registration' Plar' BURP) - This is the most widely used cooperative agreement for collecting and apportioning registration revenues from interstate motor carriers. All states were required to join the IRP system by September 30, 1996. It covers the United States and Canadian provinces. The distinguishing features of IRP are base state registration and auditing, a single license plate; and one cab card showing IRP registration. IRP is administered by the American Association of Motor Vehicle Administrators (AAMVA). IRP provides for the payment of registration fees prorated according to fleet miles operated in various jurisdictions by vehicles over 26,000 pounds gross weight, or with at least three axles. When a motor carrier initially registers with IRP, it must select a "base jurisdiction" in which to file. For fleet registration purposes, the base jurisdiction is where the motor carrier has an established place of business, where mileage is accrued by the fleet, and where operational records of the fleet are maintained or can be made available for audits. The IRP application with the base states requires, at a minimum, the number of power units, trailers, semi-trailers, and auxiliary axles. The motor carrier must also include any additional information required by the particular base state in which it is filing, and any other state through which it will be traveling. Each apportioned carrier must file an annual report to its base state, reporting mileage arid registered weight in each state for "7 ~ the preceding year as part ot its renewal application tar tne coming year's IRP registration. Under IRP, each carrier makes a single payment to the base state. Most carriers rely on their base state to calculate their IRP fees and bill them for the appropriate amount. Or, a carrier makes a single payment to the base state. That state must calculate and remit the amount due to all other IRP Glossary
member states based on the reported mileage for each jurisdiction. Carriers must maintain records of each vehicle's mileage by registered weight in every state for audit purposes. J K L layer coeval cient (a,, a2, a3~)-The empirical relationship between structural number (SN) and layer thickness which expresses the relative ability of a material to function as a structural component of a pavement. length - the total longitudinal dimension of a single vehicle, a trailer, or a semitrailer. Length of a trailer or semitrailer is measure from the front of the cargo-carrying unit to its rear, exclusive of all overhand, safety or energy efficiency devices, including air conditioning units, air compressors, flexible fender extensions, splash and spray suppressant devices, bolsters, mechanical fastening devices, and hydraulic lift gates. level of statistical significance - the probability which the user is willing to risk the error ot rejecting a valid change in M.O.E. occurrence. life-cycle costing - an economic assessment of an item, area, system, or facility and competing design alternatives considering all significant costs of ownership over the economic life, expressed in terms of equivalent dollars. loads - a weight ot quantity of anything resting upon something else regarded as its support. M maintenance - the preservation of the entire roadway, including surface, shoulders, roadsides, structures, and such traffic control devices as are necessary for its safe and efficient utilization. measures of effectiveness (M.O.E.s) - determinable quantities of what is achieved as the result of truck weight enforcement activity or program. Their application also quantifies the contribution Mat activity makes tower achievement of one ore more of the enforcement goals. mobile patrols - Mobile patrols are weight or safety inspection teams which patrol portable scales or other portable inspection equipment. They are most frequently used in conjunction with fixed weight stations, although in some states can be the sole method of enforcement. There are two types of mobile enforcement: wing and portable. Wing patrols occur on bypass routes around fixed weigh stations and can be scheduled either as a special detail or as an ongoing operation. Portable enforcement occurs in areas where there are no weigh stations, and inspectors carry semi-portable ramp scales in their vehicles. Portable enforcement with semi-portable ramp scales is also often used in conjunction with wing patrols, depending on the configuration of road network, known Glossary 6
truck travel patterns, and the availability of bypass routes. ~?~oa~ulus of subgrade reaction (k)-Westergaard's modulus of subgrade reaction for use in rigid pavement design (the load in pounds per square inch on a loaded area of the roadbed soil or subbase divided by the deflection in inches of the roadbed soil or subbase,fpsi/in.~. ~ itoring data - those annual traffic loading estimates made from data collected specifically to meet the needs of the LTPP study. (see historical estimates. Motor Carrier Management Information System (MCMIS) - MCMIS is the central federal repository of comprehensive safety data on more than 265,000 interstate motor carriers. Information is kept on a central mainframe computer and is exchanged electronically with computers in all federal field offices and MCSAP state offices using SAFETYNET software. The FHWA uses MCMIS data to set priorities and targets for conducting safety and compliance reviews, compile safety profiles of key data to support state arid federal investigations, and make safety fitness ratings available in response to public and private inquiries. MCMIS also includes data on motor carrier accidents, safety arid compliance reviews, and fitness ratings. Motor Carrier Safety Assistance Program (MCSAP) - This program was established by Title IV of the Surface Transportation Assistance Act of 1982 to get potentially unsafe drivers and imminently hazardous vehicles off the road. This was done by substantially increasing the level of safety enforcement activity. MCSAP provides grants to states for the enforcement of federal (or compatible state) motor carrier safety regulations through roadside driver and vehicle inspections. MCSAP safety inspections are conducted under the auspices of the Commercial Vehicle Safety Alliance (CVSA). motor vehicle - a vehicle which is self-propelled or propelled by electric power obtained from overhead trolley wires, but not operating upon rails. N national truck network - those interstate and other federal-ad primary highways on which commercial vehicles of the dimensions authorized by the STAA of 1982 are allowed to operate. o open/close strategy - This is a specific type of fixed weigh station operating strategy in which scales at weight stations are only open for two or three hours at any given time. After this time' a reduction in the number of overweight vehicles coming through the facility typical occurs. When this happens, the weight enforcement officials close the fixed scales and instead shift weight operations to bypass routes using portable scales stored in enforcement vehicles. operating authority - The Interstate Commerce Commission (ICC) was granted authority to regulate the interstate motor carrier industry by the Motor Carrier Act of 1935. Eligible carriers are awarded operating rights, known as operating authority, by the I.C.C. The authority specifies the products the cattier may haul, arid where it may haul them. In return for these operating rights, a cattier is obligated to provide reasonable service to the public and just, fair, and reasonable rates, 7 Glossary
classifications, and practices. Most states require that a copy of the ICC authority be filed with the state. In addition to the registration of operating authority, carriers generally also must identify the vehicles operating under those rights, present evidence of insurance and designate a resident process agent. In addition to ICC operating authority, many states require carriers to obtain operating authority from the state as well. This may be issued by transportation commissions, public service commissions, utility commissions, state corporation commissions, or state departments of transportation. In some states, multiple agencies may grant operating authority, depending on whether the carrier is an intrastate carrier or an ICC regulated interstate carrier. Most states require both intra- and interstate carriers to obtain operating authority. However, in a few states (Hawaii, Maryland, Nevada, New Jersey, and Pennsylvanian, only intrastate carriers are required to file for operating authority; seven states (Alaska, Arizona, Delaware, Florida, Vermont, Wyoming, and the District of Columbia) have eliminated this regulation entirely. Out-of-service - If a violation found during the course of a weight or safety inspection is considered to pose an immediate danger to the public, the vehicle is pulled immediately out-of-service. A driver found to have an out-of-service violation during an inspection may not drive until the applicable violation has been corrected. Similarly, vehicles with an out-of-serve violation may not be operated until the violation has been fixed. overweight - over the Federal or State legal restrictions for single axle weight, tandem axle weight or gross weight. p pavement con difion - a quantitative representation of distress in pavement at a given point pavement distress - the physical marulestations of defects In pavement at a given point. pavement maintenance - all routine actions, both responsive and preventative, which are taken by He state or over parties to preserve the pavement structure, including joints, drainage, surface, and shoulders as necessary for its safe arid efficient utilization. pavement management system - a set of tools or methods that assist decision-makers in analyzing arid designing cost-effective pavement construction, rehabilitation, arid maintenance programs. pavement performance - the trend of serviceability with load applications. pavement structure - a combination of subbase, base course, and surface course placed on a subgrade to support the traffic load and distribute it to the roadbed. pavement structure - the combination of subbase, base course, and surface course placed on an earth subgrade to support the traffic load and distribute it to the roadbed. Glossary 8
performance period - the period of time that an initially constructed or rehabilitated pavement structure will last (perform) before reaching its terminal serviceability; this is also referred to as the design period. HA ~ permit - in common usage, the written permission issued by a jurisdiction allowing specified operation. In TRP states a Trip Permit is a temporary permit issued by a jurisdiction to a motor carrier registered in another jurisdication in lieu of regular apportioned registration. Other temporary permits issued for varying lengths of time include Oversize\Overweight Hauling Permits and Temporary Fuel Use Tax Permits. The Fuel Use Tax Permit issued in Maryland for art entire year is called a decal or identification marker. portable scale - a scale of such size and weight as to be readily transportable from station to station. po~-of-entry (POE) - A port-of-entry is a fixed weigh station located at the border between states. ~ , _ . . · . . . . . . . · . . ~ . . . · . · - t seines as a gateway to a state s interstate and state highway system. States WhlCh use weigh stations as ports-of-entry have roadway configurations which have a limited number of access/egress points to that state so that carriers have few or no choices of routes which bypass the entry point. power of sfat~stica! test - the likelihood of making a correct statistical assessment the proper hypothesis is accepted. The issue is to what extent is the user willing to risk accepting art invalid change In MOE occurrence. pre-clearance - a pre-clearance system uses Intelligent Transportation System (ITS) technology to allow carriers traveling legally to bypass weigh stations. A truck carrying automatic vehicle identification (AVI) transponder taps approaches the first open weigh station after entering a .. . .. . . .. . . . . ~ .. . . . .. ... . .. . . highway corridor. A roauslue reader system in advance or the weigh station Wll1 read the Duck identification transponder. The AV! reader will pass the truck identification to the weigh station computer. The station computer checks for that truck, and finding no current data on axle weights or spacing information, directs He truck (with either a communication via the transponder or through the use of a variable message sign - VMS) to make a normal entry into the weigh station. Another AVI reader within the weigh station will again read the truck identification transponder as the truck passes and again will pass the identification to the weigh station computer. The computer will execute a processing sequence to automatically acquire axle arid gross vehicle weights, verify legal weight in that jurisdiction, and check that the operating credentials are valid. If all conditions are proper, the truck is directed back to the mainline. A "trip data packet" is created containing the just-collected truck identification and weight data and will be transmitted to the ' next downstream weigh station. As the truck approaches the next weigh station, the AVI reader again automatically reads the truck identification on the transponder, and the weigh station computer checks for a matching trip data packet, indicating that the truck has been previously weighed upstream. If so, the trip packet with weight and axle spacing data will be on file, as well as all associated credential data. All credentials are checked at the current location to determine if the truck is legal and compliant. Since the processing time for weight and credentials compliance is virtually instantaneous, while the truck is on the mainline highway approximately one-half mile before the weigh station entry ramp, if all weights and credentials are legal, the truck driver is notified via an in-cab display that he or she is precleared and authorized to continue on the highway without entering the weigh station. 9 Glossary .
prese'2t serviceability index (PSI,p)-A number derived by formula for estimating the serviceability rating from measurements of certain physical features of the pavement. Q quality control - the process used to ensure that data submitted to LTPP meets expected levels of quality. QC is usually performed by comparing submitted data against an expected Norm. R reliability - is the degree of stability exhibited when a measurement is repeated under identical conditions. With regard to truck weight enforcement MOEs, the concept is of paramount importance in recommending weight-gathering procedures which are applied to obtain the measures. regular operation' - the movement over highways of vehicles, vehicle combinations, and loads thereon, subject to the recommended limitations contained in this guide governing maximum weights and dimensions for motor vehicles and loads thereon. relevant evidence - relevant evidence is a type of illegal overweight truck enforcement which relies on the carriers' documentation to provide proof of an illegal trip. Documentation includes bills of lading, weight tickets, and other shipping documents which indicate the weight of a truck to be used. Relevant evidence laws allow a state to penalize truck drivers, truck owners, and shippers who operate a load or vehicle above the legal limits in that state. The advantage of this type of enforcement is that troopers or inspectors are not limited to identifying and citing illegal loads only while on the roadway. In addition, in states which have relevant evidence legislation, violations cited under these laws are brought to civil action instead of criminal action, which means that it is less likely that the case will be overturned (The standard of proof in civil cases is usually by a "preponderance of evidence" rather than proof beyond a reasonable doubt.). The disadvantage of relevant evidence is that it is only enforceable with gross weight limits, since shipping documents do not reflect axle weights, bridge formula weights, or tire width weights. rigid pavement - a pavement structure which distributes loads to the subgrade, having as one course a Portland cement concrete slab of relatively high-bending resistance. S SAFETYNET- This is a distributed system for managing safety data on both interstate and intrastate motor carriers and for federal and state offices to electronically exchange data on interstate carriers with MCMIS. safety review - Safety reviews are conducted on-site at company office by federal field staff, or by state staff under the MCSAP program. It inspects compliance with critical driver and vehicle safety regulations. Passenger and hazardous materials carriers are given the highest priorities for review. _ . . . . · · · . .. . Satety reviews involved examining company records to ensure that a carrier meets all safety-related regulations and has no unsafe operating practices. Each company receives a rating as satisfactory, Glossary 10
conditional, or unsatisfactory, based on the outcome of the review. Carriers with less than satisfactory ratings are told how to become compliant, but there is no enforcement power associated with safety reviews. Companies receiving satisfactory ratings do not usually receive another safety review unless the company begins to fail MCSAP safety inspections, is involved in accidents, or is the subject of a complaint. (See Compliance Review) scale tolerance - an allowable variation in the static weight of an axle load in accordance with, but not exceeding the precision of the scale involved. semitrailer - every single vehicle without motive power designed for carrying property and so designed in conjunction and used with a motor vehicle that some part of its own weight and that of its own load rests or is carried by another vehicle and having one or more load-carrying axles. ser~sifivify - the sensitivity of an MOE can establish that the applied measure produced a true indication of the sought attribute or condition. With regard to truck weight MOEs, we need experimental assurance that application of the MOE is a true indication of truck weight enforcement effects, i.e. the validity criterion is met. serviceability - the ability at time of observation of a pavement to serve traffic (auto and trucks) which use the facility. SNAP - Strategic Highway Research Program - a state sponsored research program designed to perform large-scale highway research on long-term pavement performance, asphalt, and Portland cement concrete materials, and maintenance procedures. single axle - (1) an assembly of two or more wheels whose centers are in one transverse vertical plan or may be included between two parallel transverse planes 40 inches apart extending across the full weight of the vehicle; (2) an axle on a vehicle that is separated from any pervious or succeeding axle by more than 2.44 meters (96 inches). single axle load - the total load transmitted by all wheels whose centers may be included between two parallel transverse vertical planes 40 inches apart, extending across the full width of the vehicle. single axle weight - the total weight transmitted by all wheels whose centers may be included between two parallel transverses vertical planes 1.02 meters (40 inches) apart, extending across the bill width of the vehicle. SN- (See structural number) - used to describe the strength of asphalt pavements. special permit - a written authorization to move or operate on a highway a vehicle or vehicles with or without a load of size and/or weight exceeding the limits prescribed for vehicles in regular operation. special permits - States issue permits for both regular and "special" (i.e. oversize and overweight) loads to travel off the interstate system on state roads. Special loads are indivisible, greater than 80,000 pounds gross vehicle weight, and exceed the axle weights and spacing specified by the 11 Glossary
federal bridge formula. Special permitting regulations vary widely, and sometimes conflict among states. In many cases, local geography, weather, population, or highway and bridge construction methods impose particular size and weight limits. In other cases, differences have developed over time In the absence of incentives to standardize these regulations. States have varying fee structures for special permits based on incremental vehicle weights. Except in states with weight/distance taxes and a few other states, the fees for special permits in general are intended only to cover the administrative cost of issuing the permit, and are also grossly related to the amount of pavement damage caused by oversize or overweight vehicles on state roads. States must also verify that the vehicles Heavy Vehicle Use Tax (HVUT) has been paid before a special permit can be issued. Verification of special permits is done during a weight inspection if a truck weighs more than the allowable legal gross or axle weights. special permit application - an individual, firm, partnership, corporation, or association making application for a special permit to transport a vehicle, vehicles, and/or load which is oversize or overweight and under whose authority arid responsibility such vehicle or load is transported. spread tandem - two axles that are articulated from a common attachment but are considered as two single axles rather than one tandem axle because they are separated by more than 2.44 meters (96 inches). static scale - a scale that requires that a vehicle be stopped to be weighed. steering axle - (1) the axle or axles of a motor vehicle or combination ofvehicles by which the same is guided or steered; (2) the axle to which a vehicle's steering mechanism is affixed. straight truck - a self-propelled vehicle designed and used for the transportation of property and not including tractors. structural number (SN) - an index number derived from an analysis of traffic, roadbed soil conditions, and environment which may be converted to thickness of flexible pavement layers through the use of suitable layer coefficients related to the type of material being used in each layer of the pavement structure. subbase - the layer or layers of specified or selected material of designed thickness placed on a subgrade to support a base course (or in the case of rigid pavements, the Portland cement concrete slab). subgrade - the top surface of a roadbed upon which the pavement structure and shoulders are constructed. surface course-One or more layers of a pavement structure designed to accommodate the traffic load, the top layer of which resists skidding, traffic abrasion, and the disintegrating effects of climate. The top layer of flexible pavements is sometimes called "wearing course." Glossary
T trawl c equivalence factor (e)-A numerical factor that expresses the relationship of a given axle load to another axle load in terms of their effect on the serviceability of a pavement structure. In the AASHTO Guide all axle loads are equated in terms of the equivalent number of repetitions of an ~ 8-km single axle. tandem axle - any two axles whose centers are more than 1.02 meters (40 inches) but not more than 2.44 meters (96 inches) apart and are individually attached to or articulate from, or both, a common attachment to the vehicle including a connecting mechanism designed to equalize the load between axles. tandem axle load - the total load transmitted to the road by two consecutive axles whose centers may be included between parallel vertical planes spaced more than 40 inches and not more than 96 inches apart, extending across the full width of the vehicle. fan dem axle weigh! - the total weight transmitted to the road by two or more consecutive axles whose centers may be included between parallel vertical plans spaced more than 1.02 meters (40 inches) and not more than 2.44 meters (96 inches) apart, extending across the full Width of the vehicle. TMG- Traffic Monitoring Guide (the handbook FHWA distributes that provides guidelines for collecting statewide traffic information for submittal to the federal government). tractor - a vehicle designed and used primarily as the power unit for drawing a semitrailer or trailer. trailer - every single vehicle without motive power designed for carrying property wholly on its own structure, drawn by a motor vehicle which carries no part of the weight and load of the trailer on its own wheels and having two or more load carrying axles. traveled way - the portion of the roadway for the movement of vehicles, exclusive of shoulders and auxiliary lanes. tridum axle - my three consecutive axles whose extreme centers are not more than 144 inches apart, and are individually attached to or articulated hoary, or both, a common attachment to the vehicle including a connecting mechanism designed to equalize We load between axles. truck - a motor vehicle designed, used, or maintained primarily for the transportation of property. truck tractor - a motor vehicle used primarily for drawing other vehicles and not so constructed as to carry a load other than a part of the weight of the vehicle and load so drawn. validity - the validity of a measure refers to the degree to which it actually measures what it is designed to measure. For example' measurement of truck weight does not pose a threat to validity' 3 Glossary
i.e. cargo in a container displaces the container downward; and the gravitational pull on the truck and cargo can be reliably registered on a calibrated index, which reads "pounds" or "ESALs." vehicle - a device in, upon, or by which any person or property may be transported or drawn upon a highway, except devices moved by human power or used exclusively upon stationary rails or tracks. vehicle combinafior' - an assembly of two or more vehicles coupled together for travel upon a highway. vehicle registration - all trucks are required to register with a state before traveling through that state. "Trip permits" are issued for the trip for which the truck is traveling, or a truck may be registered under the International Registration Plan (IRP). Vehicle registration trip permits are a form of temporary vehicle registration for an out-of-state vehicle that does not have registration in the state through which they are traveling, or not apportioned under IRP. All states collect fees for the registration of trucks traveling within their state. Registration fees, known as "first structure" taxes, are the oldest form of vehicle taxation, and have been in use for over 80 years. There are the second most important source of revenue (next to fuel taxes). Basically a form of capital equipment tax, these fees must be paid before a vehicle can be legally operated. vehicle titling - A motor carrier operator must show proof of ownership by registering the title of the vehicle with the state in which it is stationed. W weight-in-motion - the process of estimating a moving vehicle's gross weight and the portion of that weight that is carried by each wheel, axle, and/or axle group, by measurement and analysis of dynamic forces applied by its tires to a measuring device. Weigh-in-motion is one technology from the family of transportation technologies known as Intelligent Transportation Systems (ITS). A WIM system is a set of sensors and supporting instrumentation which measure the presence of a moving vehicle and the related dynamic tire forces at specified locations with respect to time. The system estimates vehicle weights, speed, axle spacing, and vehicle class according to axle arrangements and other parameters concerning the vehicle, arid processes, displays, and stores the information. WIM systems are installed in the pavement on highways or on bridges and determine the weight of vehicles passing over them by measuring the vertical component of dynamic force that is applied to the road surface by the wheels of the moving vehicle. There are a number of vehicle factors which affect WIM accuracy, such as how the gross vehicle weight in distributed within the truck, vehicle movement affecting the suspension system, tire tread and inflation pressure, dynamic balance and wear, and vehicle aerodynamic characteristics. Roadway factors that affect accuracy include the vertical and horizontal alignment of the roadway, and the transverse slope of each lane. WIM accuracy also suffers in adverse weather conditions such as ice arid snow at the sensor location and individual differences in the sensitivity of each Glossary 14
instrument. For these reasons, violations are not issued using WIM yet. It is almost exclusively used for either data collection, or to screen trucks on weigh station access lanes, rather than for direct enforcement activities. weight-in-motion scale - a scale that allows vehicle weights to be electronically recorded as the vehicle passes over the scale without stopping. weight station - a location equipped with weight scales at which the axle weights arid gross weights of vehicles are determined. weight violation - a single axle weight, axle group weight, or gross weight of a vehicle exceeding the maximum allowed weight for that vehicle. wheelbase - the distance between the front and rear axles of a vehicle, or the center point of contact of the front and rear wheels with the ground. wiarth - the total transverse dimension of a vehicle including any load or load-holding devices thereon, but excluding approved safety devices and tire bulge due to load. X y z 5 Glossary