TRUCK TERMS GLOSSARY A ABS (Antilock Braking System) Computer, sensors and solenoid valves which together monitor wheel speed and modulate braking force if wheel lockup is sensed during braking. Helps the driver retain control of the vehicle during heavy braking on slippery roads. A Dolly This converter dolly has an A shaped drawbar that joins at a single connection point to the trailer ahead of it. These dollies can have one or more axles and are the most common in usage. AFV (Alternative Fueled Vehicle) Vehicle powered by a fuel other than gasoline or diesel. Air Brake Air brakes use compressed air to control friction between the brake linings and the brake rotor / drum, which is mounted to the wheel. Air Brake Chamber Pressurized air from the air reservoir enters the brake chamber through the air inlet. This air presses against a diaphragm that in turn exerts force on a push rod. Air Can Trailer Slang / jargon for a pneumatic tank trailer for transporting solids in bulk. Air Compressor Powered by the engine, this device draws air in and compresses it, which increases its pressure. Air Dryer Removes dirt and moisture, reducing the possibility of corrosion and moisture in the brake system. AF (Axle to Frame) The measurement from the center of the rear axle to the end of the frame rail. Air Freight Container A small light weight cargo container often made out of fi ber glass designed to hold cargoes that are shipped in airplanes. Air Governor An air governor regulates the amount of pressure in the air system at all times by automatically starting and stopping the air compressor. Air Lift Axle (Lift Axle) An air-powered axle which, when lowered, will both convert a vehicle into a multi-axle unit and provide greater load carrying capacity. Air Reservoir System The reservoir system consists of usually cylindrical air tanks that are used to store the air from the compressor until needed. Air Ride Suspension Suspension which supports the load on air-fi lled rubber bags rather than steel springs. Compressed air is supplied by the same engine-driven air compressor and reservoir tanks which provide air to the air brake system. All-Wheel Drive A vehicle in which all the wheels are drive wheels, such as 4x4, 6x6, etc. Designed to improve on-road traction in unfavorable road conditions or for ultra high performance driving. In all-wheel drive vehicles, the transfer case receives engine power from the transmission and delivers it to the front and rear drive-shafts, then to the differentials and the wheels, reducing wheel slippage and providing greater driver control over the vehicle. Articulated Bus A bus, usually more than 55 feet in length, characterized by two connected passenger compartments that bend or fl ex in the middle and allow the bus to maneuver through curves or around corners. ATA (American Trucking Associations) A national federation of independent and autonomous truck carrier conferences and state trucking associations. Includes Regular Common Carrier Conference, National Tank Truck Carriers Conference. ATC (Automatic Traction Control) Usually an optional feature based on ABS, it prevents spinning of the drive wheels under power on slippery surfaces by braking individual wheels and/or reducing engine throttle. 1
A-Train Slang / jargon- a truck tractor pulling more than one trailer connected by A dollies. Auger A shaft with a broad spiral fl ange rotating inside a cylindrical casing to carry bulk material from one end of the shaft to the other. Augers are used to unload cargoes such as grain from grain trailers. Auto Carrier Specialized multi-decked trailer and/or power unit specifi cally used to transport automobiles. AVI (Automatic Vehicle Identification) System combining an on-board transponder with roadside receivers to automate identifi cation of vehicles. Uses include electronic toll collection and stolen vehicle detection. AVL (Automated Vehicle Location) Class of technologies designed to locate vehicles for fl eet management purposes and for stolen vehicle recovery. Infrastructure can be land-based radio towers or satellites. Axle Structural component to which wheels, brakes and suspension are attached. Axle designations such as 4x2, 6x4, etc.: the number of wheels followed by the number of wheels driving, each axle assumed to have one wheel at each end, e.g., 6x4 is 6 wheels total, 4 driving, thus, a 3-axle power unit with 2 drive axles. Drive axles are those with powered wheels. Front axle is usually called the steer axle. Pusher axles are unpowered and go ahead of drive axles. Rear axles may be drive, tag or pusher types. Tag axles are unpowered and go behind drive axles. Axle Weight Amount of weight carried by one axle. B Baffle A wall or partition inside a liquid tank that inhibits the fl ow of fl uids reducing the slosh effect that liquid tankers experience. BBC (Bumper to Back of Cab) The distance from the front bumper to the back of the truck cab. B Dolly A fi fth wheel mounted on one or more axles that are permanently attached and extend off the rear of a semitrailer, most commonly used on fl atbeds or tank trailers. Beavertail A hinged ramp(s) on the end of a fl atbed trailer enabling vehicles or heavy equipment to drive onto the trailer. These ramps can be powered by a hydraulic mechanism. Belly Bin Boxes attached under the fl oor of a trailer. May carry cargo, but more often used for carrying spare parts. Belly Dump Another name for a HOPPER BOTTOM trailer, both empty their load from underneath via gravity. Bill of Lading Itemized list of goods contained in a shipment. A contract between the shipper and the carrier that includes freight origin and destination, description, and weight. Blind Spot Areas around a commercial vehicle not visible to the driver either through the windshield, side windows, or mirrors. Bobtail Slang / jargon a tractor operating without a trailer. Body The payload-carrying or work-performing structure that s mounted directly on a truck chassis. Bogie (also spelled bogey) Assembly of two or more axles, usually a pair in tandem. Boom A lifting mechanism. May be mounted on or as part of the cargo body of a truck. Booms are common on utility trucks or fl atbeds. Booster (Axle or Dolly) Usually at the rear of a truck and employs hydraulics to shift some of the load weight onto the vehicle s main axles. Bottle Refers to the cargo tank of a truck or trailer designed to carry liquefi ed or compressed gases. Examples include bottled gas, propane, and butane. Bottom Dump Dry bulk bodies which empty by means of gravity alone through the bottom. Sometimes referred to as hopper bottoms or belly dumps. 2
Brake Horsepower (bhp) Engine horsepower rating as determined by brake dynamometer testing. (see Horsepower) Bridge Formula A bridge protection formula used by federal and state governments to regulate the amount of weight that can be put on each of a vehicle s axles, and how far apart the axles (or groups of axles) must be to legally carry a given weight. B-Train Slang / jargon a truck tractor pulling two semi-trailers where the second trailer sits on a fi fth wheel that is permanently attached and extends off the rear of the lead trailer. Most commonly used on fl atbeds or tank trailers. The B train is considered a more stable double trailers confi guration. Bulk Cargo Loose and unpackaged, sometimes referred to as aggregate cargo. Bulk Hauler Vehicle that carries a large quantity of a single dry, liquid or gaseous commodity such as various types of grains, chemicals, petroleum products, etc. Bulkhead Wall-like structure used at the front of a fl atbed or back of the power unit to protect against damage from shifting cargo, or a wall inside any trailer that partitions the load. Bunk Cradle-like metal up-right brackets mounted on a log truck or trailer to hold the logs. Sometimes referred to as bolsters. Bunk Slang-Jargon-See Sleeper. C CA (Cab to Axle) Measurement from the back of the cab to the center of the rear axle. Cab The enclosed compartment in a vehicle in which the driver sits. Cab & Chassis (CC or C&C) Most trucks are sold as a frame and running gear (chassis) with a cab. The cargo body or fi fth wheel is added by the purchaser or a body builder. Cab Forward Similar to a cab-over in that the cab is positioned ahead of the engine. Most commonly seen on refuse trucks and some construction equipment. Cab-over (Cab-Over-Engine, COE) Truck or tractor design in which the cab sits over the engine on the chassis. The cab-over is identifi ed by the windshield being located directly over the front bumper and driver more or less directly over the steering axle. Cargo Weight Combined weight of all loads, gear and supplies on a vehicle. Cartage Company Company that provides local (within a town, city or municipality) pick-up and delivery. Cast Spoke Wheel Wheel with fi ve or six spokes originating from a center hub. The spoked portion, usually made of cast steel, is bolted to a multiple-piece steel rim. CB (Citizens Band Radio) Two-way radio for which no license is required by the Federal Communications Commission (FCC). Long beyond its heyday in the 70s, CB is still used by truckers and motorists for everything from traffi c condition reports to emergency calls to idle chatter. C-Channel A frame rail created by stamping steel or extruding aluminum alloys into lengths with a C shaped cross-section. CDL (Commercial Driver s License) License which authorizes an individual to operate commercial motor vehicles and buses over 26,000 pounds gross vehicle weight. C Dolly This converter dolly has two drawbars and attaches at two connection points to the trailer ahead of it. These dollies can have one or more axles and are considered more stable than the common A dolly. CE (CF, CeoF) Distance from back of a truck s cab to the end of its frame. CG (Center of Gravity) Weight center or balance point of an object, such as a truck body. Calculated to help determine optimum placement of truck bodies on chassis. 3
Charge Air Cooler Used in conjunction with a turbocharger, it is a means by which the effi ciency of the turbocharger can be increased. Charge air coolers allow heated air to be cooled before entering the engine. Cool, dense air creates more effi cient combustion. Think of this as a radiator for the engine s air intake. Charter Bus A bus that is operated on a for-hire basis, usually providing round-trip service for a tour group or an outing, either on an ad hoc or scheduled basis. Chassis The framework or foundation of the vehicle, consisting of its frame rails, cross-members, suspensions, and drive-train everything except the cab. Cheater Axle (Slang) for a lift axle or an air-powered axle which, when lowered, will both convert a vehicle into a multi-axle unit and provide greater load carrying capacity. Chassis Weight (Curb Weight, Tare Weight) Weight of the empty truck, without occupants or load. Club Cab Extended Cab A two door truck cab with a back seat behind the front seats. Clutch Connects or disconnects the engine power from the transmission and driveline to allow the driver to select gears based on the current driving situation. When the clutch pedal is disengaged, the power produced by the engine is transmitted through it to the transmission. When the clutch pedal is engaged, such as during idling, the power is not transmitted to other driveline components. CMV (Commercial Motor Vehicle ) A motor vehicle or combination of motor vehicles used in commerce to transport passengers or property if the motor vehicle: 1) has a gross combination weight rating greater than or equal to 26,000 lb. including a towed unit with a gross vehicle weight rating of at least 10,000 lb.; or 2) has a gross vehicle weight rating of at least 26,001 lb.; or 3) is designed to transport 16 or more passengers including the driver; or 4) a motor vehicle of any size that transports hazardous materials of any kind. CNG Compressed natural gas. COE See Cab-over. Combination Vehicle A vehicle made up of two or more separate units hooked together, such as a tractor-semi-trailer combination. Also called an ARTICULATED vehicle since units pivot at the coupling point. Commodity Anything bought and sold. Common Carrier Freight transportation company which serves the general public. May be regular route service (over designated highways on a regular basis) or irregular route (between various points on an unscheduled basis). Interstate common carriers must hold a certifi cate issued by the Interstate Commerce Commission which limits service to a specifi c geographical area. Compactor A device used to compact things, particularly garbage. Compensated Intracorporate Hauling Freight transportation service provided by one company for a sister company. Consignee The person or fi rm designated to receive freight that has been shipped. Consignor The person or fi rm responsible for shipping a particular freight. Container (Shipping Container) Standard-sized rectangular box used to transport freight by ship, rail and highway. International shipping containers are 20 or 40 feet long, conform to International Standards Organization (ISO) standards and are designed to fi t in ships holds. Containers are transported on public roads atop a container chassis towed by a tractor. Domestic containers, up to 53 feet long and of lighter construction, are designed for rail and highway use only. Container Chassis Single-purpose semi-trailer consisting of a frame (no fl oor, sides or roof) with locking devices for securing and transporting a shipping container. Contract Carrier A company that engages in for-hire transportation of property under individual contract or agreement with one or a limited number of shippers. Conventional Engine forward of cab in power unit. 4
Converter Dolly An undercarriage assembly with one or more axles, a fi fth wheel, and a tongue, used to convert a semi-trailer to a full trailer. Crew Cab A four door truck cab with front and back seats. Cross-members Create the bridge between the outer frame rails, tying the chassis together and providing additional load bearing capacity. Cross-members are formed from stamped or extruded beams in the form of C-Channels, I-beams or hat sections. Cube (Cubic Capacity) Interior volume of a truck body, semi-trailer or trailer, measured in cubic feet. Can also be used to refer to a pallet of concrete blocks. Cube Out When a trailer is full by volume, but there is weight capacity to spare. Refers to cubic feet of space. Cube Van Typically a straight truck with a van style cargo body where the width and height of the cargo body exceed that of the truck cab. Curb Weight See Chassis Weight. D Day Cab A truck or tractor without a sleeper berth. Typically used for day trips or local routes. Dead Axle Non-powered rear axle on tandem truck or tractor. Deck Set (Slang) for piggyback hauled trucks. See Piggyback. Dead-Heading A trip where the tractor pulls an empty trailer or a trailer loaded with cargo that generates no revenue. (Slang-Pulling sailboat fuel) Demountable Rim Multi-piece steel wheel rim assembly which is bolted to a spoke hub. Demountable rims are still in use, though they have been replaced in many applications by the simpler disc wheel. (see Cast Spoke Wheel) Disc Wheel Single-piece rim/wheel assembly of stamped and welded steel or forged aluminum, anchored by 8 or 10 nuts to a hub. A Budd wheel is a ten-hole, stud-piloted disc wheel; a design originated by the Budd Corporation. Displacement (Piston Displacement) Sum of the volumes swept by an engine s pistons as they travel up and down in their cylinders. Based upon bore (diameter of cylinder) and stroke (distance traveled by piston). Expressed in liters or cubic inches. Dolly See Converter Dolly. Doubles (Twins, Twin Trailers) Combination of a tractor and two semi-trailers connected in tandem by a converter dolly. Double Drop Deck A trailer, usually a fl atbed, with a fl oor set at three different heights, it steps down towards the middle and then steps back up at the rear. Sometimes referred to as a STEP DECK. Drag Link Part of the steering system. As the driver turns the steering wheel the back-and-forth motion of the hydraulic unit is sent to the wheels through the pitman arm, center link and the tie rods, which are connected to the wheels. Draw Bar A metal bar that connects a truck and trailer. Sometimes referred to as the tongue of the trailer. Drive Axle Any axle that carries power from the engine to the wheels that propel a truck or tractor. See AXLE. Driveline All the components which together transmit power from the transmission to the drive axle(s). These consist of at least one driveshaft (propeller shaft) with a universal joint at each end. Driveshaft A long, extremely durable steel tube that is fi tted with u-joints and a slip joint. There are usually two to a driveline. Drive-train (Power-train) The drive-train includes all the components (engine, transmission, driveshaft, differential and drive axles) which transmit the engine s power to the rear wheels. 5
DRL (Daytime Running Lights) System that automatically turns on a vehicle s low beam headlights when the parking brake is released and the ignition is on. Dual Wheels Four wheels per axle rather than two. Dump A cargo body with a hydraulic, electric, or mechanical lifting mechanism that tilts to unload cargo. DUMP includes side dumps, walking dumps, fl atbed dumps, and dump trucks with snow plows or blades. Dumpster A large metal container for garbage. The term is sometimes used to describe refuse trucks. Dumpsters are different from roll-off containers. A dumpster is usually kept at a garbage collection point and not carried on a refuse truck. Dunnage Loose materials (like padding) used around cargo to prevent damage. E EDI (Electronic Data Interchange) The business-to-business interconnection of computers for the rapid exchange of a wide variety of documents, from bills of lading to build tickets at auto plants. Eighteen Wheeler (Slang) A three axle tractor pulling a two axle semi-trailer or a two axle tractor pulling a three axle semi-trailer. Electronic Brake System (EBS) Brake system that uses an electronic signal instead of a pneumatic signal to monitor and actuate the brakes. Commonly referred to as a brake-by-wire system. During an emergency stop, EBS also activates the Antilock Brake System (ABS). Electronic Trip Recorder A device for recording data on a vehicle s performance, originally designed for monitoring and optimizing engine performance, in recent years GPS systems have been added to enable dispatchers to geo-locate their trucks and many trip recorders maintain HOS data, eliminating the need for driver maintained logbooks. Engine Retarder An engine retarder is any wear-free supplementary braking system that operates separately of the wheel brakes, allowing vehicles to operate within safe speed limits, even on steep grades, without creating brake fade in the primary braking system. While engine retarders act as brakes, they operate as part of the engine exhaust system. Primary retarders are fi tted between the engine and transmission and secondary retarders are placed between the transmission and the drive axle(s). Also called Jake brakes or compression brakes. EV (Electric Vehicle) Vehicle powered by electric motor(s) rather than by an internal combustion engine. Most common source of electricity is chemical storage batteries. Exempt Carrier Company which transports commodities exempted from Interstate Commerce Commission (ICC) economic regulation. Expandable Flatbed or pole trailers that can be expanded beyond their regular length to carry larger shipments. Extended Cab - See Club Cab. F Fan Clutch Operates using a switch regulated by thermostat readings. Once engine temperature has reached a preset threshold, as measured by a sensor in the engine coolant, the fan will be activated to provide additional cooling. Fifth Wheel Coupling device attached to mounted on the rear of a tractor s chassis or dolly which supports the front of a semitrailer and locks it to the tractor or dolly. The fi fth wheel s center is designed to accept a trailer s kingpin, around which the trailer and tractor or dolly pivot in turns. For-Hire Carrier Company in the business of transporting freight belonging to others. Flange Upper and lower horizontal surfaces of a frame rail. 6
Flatbeds or Platforms Open-bed trailers that haul heavy goods not easily loaded into vans, such as construction equipment, lumber and industrial machinery. Allows loading/unloading from the sides. Frame Rails Two parallel rails that run the length of the vehicle on either side and provide the majority of its weight-bearing capacity. Created by stamping steel or extruding aluminum alloys into lengths with a C or L shaped cross section. Front-Loader A refuse truck that is loaded at the front usually has hydraulic arms that lift dumpsters over the cab dumping their contents into a bin with some kind of compacting mechanism. Arms must be included in truck length. Fuel Any type of fuel; can be gasoline, diesel, CNG (compressed natural gas), LPG (liquefi ed petroleum gas, also referred to as propane), or other (electric, hybrid etc.). Full Trailer A full trailer is a trailer with axles in the front as well as the rear. It can stand without support. Full trailers are coupled to straight trucks and to the rear of semi or full trailers by a tongue or drawbar. Full trailers are seldom used alone with tractors. G Garbage (Refuse) A cargo body style typifi ed by Garbage trucks that often have hydraulic packing mechanisms or hydraulic arms for lifting dumpsters. Included are roll-offs, vehicles used for transporting refuse containers. Roll-offs have rails or a fl at bed and a hoist for loading and unloading the refuse container. GAWR (Gross Axle Weight Rating) Maximum weight an axle is rated to carry by the manufacturer. Includes both the weight of the axle and the portion of a vehicle s weight carried by the axle. GCW (Gross Combination Weight) Total weight of a loaded combination vehicle, such as a tractor-semi-trailer or truck and full trailer(s). Geared Speed Calculated vehicle speed at the engine s governed rpm in each transmission gear, or (commonly) in top gear. Gear Ratio Number, usually expressed as a decimal fraction, representing how many turns of the input shaft cause exactly one revolution of the output shaft. Applies to transmissions, power takeoffs, power dividers and rear axles. Example: If 2.5 revolutions of an input shaft cause one revolution of the output shaft, the gear ratio is 2.5:1. Glider Kit Usually a cab and chassis without an engine or rear axles. Used to rebuild a wrecked tractor. Gooseneck A hitch resembling the neck of a goose. Can be fi fth wheel or an inverted ball hitch attachment. Both straight trucks and tractor-trailer rigs can use goosenecks. Grade Steepness of a grade, expressed as a percentage. Example: A vehicle climbing a 5% grade rises 5 feet for every 100 feet of forward travel. Gradeability Vehicle s ability to climb a grade at a given speed. Example: A truck with a gradeability of 5% at 60 mph can maintain 60 mph on a grade with a rise of 5%. Gross Out Refers to gross weight. You may still have available hauling space in your trailer, but are unable to take on more weight per legal limits. GVW (Gross Vehicle Weight) Total weight of a vehicle and everything aboard, including its load. GVWR (Gross Vehicle Weight Rating) Total weight a vehicle is rated to carry by the manufacturer, including its own weight and the weight of its load. H Hazmat Hazardous materials, as classifi ed by the U.S. Environmental Protection Agency (EPA). Transport of hazardous materials is strictly regulated by the U.S. Department of Transportation. Headache Rack Heavy protective barrier, or bulkhead mounted behind the tractor s cab. Designed to prevent headaches caused by load shifting forward from the trailer and crushing the cab. 7
Head Ramp An apparatus attached over the cab of tractors to carry motor vehicles as freight. Auto carriers may or may not have HEAD RAMPS. Height Control Valve Part of an air suspension system. As freight is loaded onto the truck, the air bag system s height control valve opens and allows compressed air from the brake system to fl ow into its air bags causing the tractor/trailer to compensate for the added weight and maintain a steady ride height. When the cargo is unloaded, the valve releases air from the bags, allowing the vehicle to retain its optimal height. Hoist Refers to the lifting mechanism under cargo bodies that dump. Hopper Bottom An open top cargo body capable of discharging its load through a bottom opening without tilting. Sometimes referred to as bottom dumps. Horsepower (hp) Measure of power (the amount of work that can be done over a given amount of time). One horsepower is defi ned as 33,000 foot-pounds of work in one minute. Example: Lifting 33,000 pounds one foot in one minute, or lifting 3300 pounds ten feet in one minute. Horsepower, Gross Laboratory Tested horsepower of a bare engine without fan, water pump, alternator, exhaust system or any other accessories. Horsepower, SAE Net Horsepower capability of an engine with full accessories and exhaust system. Test procedures per standards of Society of Automotive Engineers (SAE). Hot Shot (Slang) - 1) a local freight hauler; 2) a one ton truck equipped with a fi fth wheel for pulling light weight trailers. Hours-Of-Service Federal safety regulations which govern the hours of service of commercial vehicle drivers engaged in interstate trucking operations. Hydraulic Brakes A brake system that uses hydraulic fl uid to activate the brakes. When the pedal is pressed, hydraulic fl uid forces the pistons to put pressure on the brake pads which rub against the brake disc and cause enough friction to stop. Since a hydraulic system simply boosts the mechanical force exerted by the driver, its use is limited to cars and medium-sized trucks. For heavy duty trucks carrying substantial payloads, the air brake system is most often used. I ICC (Interstate Commerce Commission) The federal body formerly charged with enforcing Acts of Congress affecting interstate commerce. The ICC was decommissioned in 1993. ICC Bumper Typically made out of 3 to 4 steel channel stock, usually about 75% of the width of the trailer, suspended half the distance from the trailer floor to the pavement with a strong enough bracing to meet federal regulations governing underride guards. In-Line Engine In-line engines are named for the shape that their cylinders form when you look at the engine from either end. Configuration where all cylinders are in a single row. Inter-Axle Differential Used on tandem axle vehicles and on all-wheel drive vehicles. Just as the standard axle differential splits the engine s power to the two axle halves, the inter-axle differential splits the power between the tandem axles. The inter-axle differential compensates for tire slippage, mismatched tires between axles and differences in wheel rotation during cornering. Intermodal Container A cargo container designed for high-speed transfer of cargoes between different transportation modes. Typically seen around harbor ports, railway yards, and cargo storage facilities. Interstate Trucking commerce crossing state lines. Intrastate Trucking commerce within the same state. IVHS (Intelligent Vehicle Highway Systems) Blanket term for a wide array of technologies, including electronic sensors, computer hardware and software and radio communications. The purpose of IVHS is to increase efficiency of use of existing highways, reducing travel time, fuel consumption, air pollution and accidents. There are five functional areas: Advanced Public Transportation Systems (APTS) Advance Traffic Management Systems (ATMS) Advance Traveler Information Systems (ATIS) Advanced Vehicle Control Systems (AVCS) Commercial Vehicle Operations (CVO) A more recently coined term, Intelligent Transportation Systems (ITS), encompasses both IVHS and modes of transportation other than highway, such as rail. 8
J Jackknife To place the trailer at a very sharp angle to the tractor. Jake Brake See also Retarder. A device that increases braking effi ciency by manipulating the engine valves to create engine drag, also referred to as an engine retarder. Slang term for an engine brake, specifi cally manufactured by Jacobs compression brake. Jeep Dolly A heavy-duty goose neck dolly usually with 2 or more axles that support the front of a cradle frame for transporting large objects or a heavy-duty lowboy trailer. JIT (Just-In-Time) Manufacturing system which depends on frequent, small deliveries of parts and supplies to keep on-site inventory to a minimum. K Kingpin (axle) Pin around which a steer axle s wheels pivot. Kingpin (trailer) Attaching pin on a semi-trailer that attaches to and pivots within the fi fth wheel of a tractor or converter dolly. Kompensator This is a fi fth wheel that tilts side-to-side as well as up and down. It is used with trailers with rigid frames that travel offroad, such as tankers or lowboys. L Landing Gear Retracting legs which support the front of a semi-trailer when it is not coupled to a tractor. LCV (Long Combination Vehicle) In general, vehicles longer than a standard doubles rig (tractor and two 28-foot semi-trailers). Examples of LCVs are: Twin 48-foot trailers; triple 28-foot trailers. Lease Truck companies sometimes lease trucks or trailers from leasing companies. Lessee Company or individual which leases vehicles. Lessor Company which leases vehicles. Lift Axle Extra, unpowered axle needed only when the vehicle is loaded, allowing it to meet federal and state vehicle weight standards. The lift axle is mounted to an air spring suspension that raises the axle when it is not required. Liquids in Bulk This cargo category describes the contents of liquid tanks that are not otherwise packaged. Examples include brine, gasoline, whiskey mash, milk, driller s mud (90% water), oil, septic waste, molten sulfur, sulfuric acid, water, tallow, live fi sh if transported in water. Livestock Carrier This trailer cargo body style typically has slotted or slatted sides designed for the transportation of farm animals. It may have a double deck. These trailers sometimes have possum bellies, compartments in the bottom for holding smaller animals. Loader (1) an off road vehicle with a large bucket or shovel on the front to move material, particularly dirt or debris. (2) refers to a hydraulic mechanism mounted on a trailer or behind the cab of a truck or tractor used to load cargo onto the trailer or truck. Some logging industry trucks are equipped with log loaders for loading fresh cut logs. Locking Differential Locks left and right sides of an axle for improved traction. Logbook Book carried by truck drivers in which they record their hours of service and duty status for each 24-hour period. Logging Trailers Some pole trailers consist of a set of axles with a cradle to hold logs and a pole attached to the rear of a power unit. Others are skeletally framed. Some have double decks. Most will have cradle-like features called BUNKS to hold the logs in place. Lowboy Open fl at-bed gooseneck trailer with a deck height very low to the ground, used to haul construction equipment or bulky or heavy loads. LPG Liquid propane gas. LTL (Less-Than-Truckload) A quantity of freight less than that required for the application of a truckload (TL) rate; usually less than 10,000 pounds. 9
LTL Carrier Trucking company which consolidates less-than-truckload cargo for multiple destinations on one vehicle. M Michigan Doubles A combination vehicle consisting of a tractor pulling two trailers with a total of 11 axles, typically for hauling gravel (dump trailers) or steel (fl atbed trailers). Multi-Leaf Spring A type of truck suspension that is a combination of fl at and/or slightly tapered leaf springs stacked to obtain a given height and fl ex rate. N Neck Refers to the non-load bearing coupling portion of a trailer. Net Used in weighing terminology, refers to cargo weight. (Tare = unloaded, Net = cargo, Gross = Tare + Net). NHTSA (National Highway Traffic Safety Administration) Regulatory part of the U.S. Department of Transportation. No Tilt Unlike a typical fi fth wheel, the kingpin on the trailer tilts, rather than the fi fth wheel. Typically used for aluminum frameless end dump trailers. O Ocean Container A completely enclosed, often water tight container designed to be loaded onto ocean freighters to carry commodities overseas. Oilfield Body Heavily constructed platform-type body equipped with instruments and machinery for oil drilling. Open Top Van A cargo body style with sides but without a permanent fi xed, solid top. Operating Authority The entity responsible for a truck being on the roadway. An example would be if you own the truck and are transporting your own cargo then you would be the operating authority; or if you needed a commodity shipped and hired a trucking company to transport it for you, then the trucking company would be the operating authority. A rule of thumb in determining operating authority is to examine who owns or is responsible for the cargo. Outrigger Leg-like extensions used on the front and/or rear of machinery to improve stability. Also, structural load-carrying members attached to and extending from the main frame of a trailer. Overdrive Gearing in which less than one revolution of a transmission s input shaft causes one turn of the output shaft. Example: A transmission with an overdrive top gear has a ratio of 0.70 to one. Turning the input shaft 0.7 revolutions causes 1.0 revolution of the output shaft. Over-the-Road Travel from one city to another, as distinct from travel in and around the vehicle s base. Owner-Operator A for-hire carrier who both owns and drives a vehicle and serves as the operating authority. P P&D Pickup and delivery. Payload Weight of the cargo being hauled. Peddle Run Truck route with frequent delivery stops. Pigtail Cable used to transmit electrical power from the tractor to the trailer. So named because it is coiled like a pig s tail. Piggyback/Tow-away Refers to motor vehicles being carried piggyback on a power unit. The trucks being carried have their front axles off the ground resting on the vehicle in front. Several vehicles may be hitched together in this way. This category is also used for wreckers towing a vehicle. Piggyback also refers to the way empty log trailers are carried on the bed of a tractor such that no axles touch the ground. Also may refer to other kinds of vehicles carried on the rear of a power unit in a manner that axles do touch the road. See also DECK SET. 10
Pintle Hook Coupling device used in double trailer, triple trailer and trucktrailer combinations. It has a curved, fi xed towing horn and an upper latch that opens to accept the drawbar eye of a trailer or dolly. Pitman Arm A bracket attached to the steering gear box that transfers the movement of the steering wheel to turn the front wheels. Planetary Gearing Automatic transmissions use a torque converter to multiply the available torque as the engine speeds up. Power from the torque converter then enters an automatic transmission s planetary gearing. The cosmic reference comes from the arrangement of the gears, which is set up like the sun with several planets revolving around it. Using a movement principle similar to sliding gear manual transmissions, these planetary gears are engaged by a series of multiple disc clutches. Ply Rating (PR) Relative measure of tire casing strength. A ply is a layer of rubber-coated parallel cords, which together with steel or nylon form the body of a tire. A multiple ply tire may only indicate the equivalent strength of the tire wall rather than the number of layers in the tire. Pole Trailers A logging trailer. Consists of a set of axles with a cradle to hold logs and a long, sometimes adjustable pole attached to the rear of a power unit. Usually has bunks for holding logs. The center portion of the trailer may be adjustable in order to accommodate loads of different lengths. Pole Truck (1) also, WINCH TRUCK - it has lifting equipment for lifting poles in oilfi eld service and contracting. It can have an A- frame. (2) Sometimes refers to a fl atbed with bunks. Pony Axle (Slang) for a smaller diameter wheel attached to a lift axle. Possum Belly Trailer A drop center livestock trailer. Powertrain See Drivetrain. Power Unit A truck, or the part of a combination that has the engine. Private Carrier A company which maintains its own trucks to transport its own freight. The principal business activity of a private carrier is not transportation. (see For-Hire Carrier) PSI (Pounds Per Square Inch) In trucking, unit of measurement for tire air pressure, air brake system pressure and turbocharger boost. PTO (Power Takeoff) Device used to transmit engine power to auxiliary equipment. A PTO often drives a hydraulic pump, which can power a dump body, concrete mixer or refuse packer. Some designs mount to a standard opening on the transmission, while others attach at the front or rear of the engine. Pull Trailer Short, full trailer (supported by axles front and rear) with an extended tongue. Pulpwood Logs (usually shorter and smaller in diameter) used for making pulp to manufacture paper. Pup Trailer A short semi-trailer between 26 and 32 feet long, with a single axle. Used in combination with a dolly and another semi-trailer to create a twin trailer. Sometimes used to refer to a short semi-trailer not in twin combination. Sometimes a pull trailer is referred to as pup. See PULL TRAILER. Pusher Axle The non-powered axle placed ahead of a powered rear axle on a vehicle. R Racks Removable wood or metal wall sections attachable to fl atbed trailers to make sides for confi ning loads. Railway Container A cargo container that can be loaded or stacked on a railroad fl at car. Rat Hole Service Oilfi eld vehicle- refers to drilling rigs. Rear Loader A refuse truck that is loaded at the rear usually with some kind of compacting mechanism. Reefer Refrigerated trailer or truck with insulated walls and a self-powered refrigeration unit. Most commonly used for transporting food. 11
Refuse A cargo body style synonymous with garbage trucks that often have hydraulic packing mechanisms or hydraulic arms for lifting dumpsters. Included are roll-offs, vehicles used for transporting refuse containers. Roll-off refuse trucks have rails or a fl at bed and a hoist for loading and unloading the refuse container. Relay (Relay Driving) Common practice in the less-than-truckload industry, in which one driver takes a truck for 8 to 10 hours, then turns the truck over to another driver, pony express style. REPTO (Rear Engine Power Take-Off) A PTO mounted at the rear of the engine, which powers an auxiliary device using the engine power. Retarder Device used to assist brakes in slowing the vehicle. The most common type of retarder on over-the-road trucks manipulates the engine s valves to create engine drag. (This type is commonly referred to as Jake Brake because the predominant manufacturer is Jacobs Vehicle Equipment Co.) Other types of retarders include exhaust retarders, transmission-mounted hydraulic retarders and axle-mounted electromagnetic retarders. Rig Trucking jargon for a truck or tractor-trailer combination. Road-Railer Semi-trailer specially designed to travel both on highway and on rails. Rocky Mountain Doubles A combination vehicle consisting of a tractor pulling a 45 to 48 foot semi-trailer and second shorter semi-trailer (usually 28 feet in length). Rolling Radius Tire dimension from center of the axle to the ground; measured with tire loaded to rated capacity. Used in calculating geared speed. Roll-Off Container Typically an open top container designed for transporting solids in bulk, often used as REFUSE CONTAINERS. The vehicles used for transporting roll-off containers have rails or a fl at bed with a hydraulic hoist for loading and unloading these large containers. RPM (Revolutions Per Minute) Measure of the speed at which a shaft spins. Most often used to describe engine crankshaft speed. Indicated by a tachometer. Runaway Truck Ramp Emergency area adjacent to a steep downgrade that a heavy truck can steer into after losing braking power. Usually two or three lanes wide and several hundred feet long, the ramp is a soft, gravel-fi lled pathway which absorbs the truck s forward momentum, bringing it to a safe stop. Depending on the surrounding terrain, the ramp may be level or run up or down hill. S S Cam The S-shaped part of the brake mechanism that expands the brake shoes against the brake drum when rotated by air or hydraulic pressure. Scissors Lift A cargo body which is used to lift materials to a higher surface, such as lifting shingles to a roof. Semi-trailer Truck trailer supported at the rear by its own wheels and at the front by a fi fth wheel mounted to a tractor or dolly. A semi-trailer has no front axle and cannot stand without support. Semi-trailers are pulled by tractors only. Setback Axle Front steering axle moved rearward from the generally accepted standard position. Advantages: Shorter turning radius and more of a vehicle s weight shifted to front axle. Shipping Weight Dry weight of a truck including all standard equipment, but excluding fuel and coolant. Side Loader A refuse truck which is loaded from the side. Single Drop Trailer A type of fl atbed trailer. The rear is closer to the ground than the front. Also called SINGLE DROP PLATFORM. Single-Source Leasing Service in which companies can lease drivers and trucks from the same source, rather than having to procure them from different companies. Slack Adjuster A part of the air brake system. Specifi cally, the slack adjuster compensates for wear in the brake linings, ensuring that the distance between the brake linings and drums is always the same. Both manual and automatic slack adjusters are available. 12
Sleeper Sleeping compartment mounted behind a truck cab, sometimes attached to the cab or even designed to be an integral part of it. Sleeper Team See Team. Sliding Fifth Wheel A fi fth-wheel assembly capable of being moved forward or backward on the tractor to adjust the load distribution on the tractor and the overall length of the rig. Sliding Tandem (Slider) Mechanism that allows a tandem axle suspension to be moved back and forth at the rear of a semi-trailer, for the purpose of adjusting the distribution of weight between the axles and fi fth wheel. Speedability Top speed a vehicle can attain as determined by engine power, engine governed speed, gross weight, driveline effi ciency, air resistance, grade and load. Spoke Wheel See Cast Spoke Wheel. Spread Axle (Spread Tandem) Tandem axle assembly spaced further apart than the standard spacing of 54 inches. The U.S. federal bridge formula favors trailer axles with an eight or nine foot spread by allowing higher weight than on tandems with standard spacing. Stake Body A fl atbed with sides or stakes to retain the load. Steerable Dolly Used in transporting extremely long objects, some can be steered remotely from the cab. Steering Axle An axle through which directional control of the vehicle is applied. It may be powered or not and there may be more than one steering axle on a single unit. Step Bumper A bumper that can also function as a stepping platform either into or out of a cargo body, usually these bumpers are mounted relatively close to the ground. Step Van A lightweight delivery truck designed so the driver can step into and out of the cab as well as into the rear cargo area. Stinger Fifth Wheel Seen most commonly as the connection point for autocarriers, but are also seen on some logging rigs. The inverted fi fth wheel is mounted behind the rear axles, at the very end of the tractor, less than a foot off the ground. Straight Truck See Truck. A single unit vehicle capable of carrying cargo. Examples include refuse, tank, and dump trucks. Straight trucks may or may not pull trailers. Synchronized Transmission Transmission with built-in mechanisms to automatically equalize the speed of its gears to allow smooth shifting without the need to double-clutch. Switching Tractor See Yard Horse. T Tag Axle See Axle. A non powered axle located behind the drive axle. Tag or Tagalong Trailers Usually single axle equipment like generators, cement mixers, or wood chippers. Tandem Axle Refers to a pair of axles at the rear of the power unit (tractor or straight truck) or trailer. For power units, if described as a tandem, usually indicates the number of drive axles on the power unit. Tanker An enclosed cargo body designed solely for the transportation of fl uid or gaseous commodities in bulk. Not to be confused with trailers which are designed for carrying dry bulk products. Tanker - Dry Bulk Sometimes called air-can trailers. Used exclusively for hauling dry bulk material. Cargo is emptied pneumatically. Tanker Liquid/Gas A cargo body style characterized by tankers which can carry only liquids or gases in bulk. Taper-Leaf Spring A curved spring design which distributes the load evenly throughout the length of the spring, putting material only where needed. Tare Weight See Chassis Weight. The weight of a vehicle without a load. 13
Team (Driver Team) Team of two drivers who alternate driving and resting. TEU (Twenty-Foot Equivalent Unit) Standardized unit for measuring container capacity on ships, railcars, etc. TL (Truckload) The quantity of freight required to fi ll a trailer; usually more than 10,000 pounds. TL Carrier Trucking company which dedicates trailers to a single shipper s cargo, as opposed to an LTL (Less Than Truckload) carrier which transports the consolidated cargo of several shippers and makes multiple deliveries. TOFC (Trailer On Flatcar) Method of moving cargo which involves transporting semitrailers on railroad fl at cars. Torque Torque is a turning or twisting effort. In truck applications, it refers to the force that an engine delivers to turn the drive shaft. Torque also refers to the measurement of that force, whether or not it actually produces movement. Torque Converter Automatic transmissions use a torque converter to multiply the available torque as the engine speeds up. Power from the torque converter then enters an automatic transmission s planetary gearing. Toter A power unit designed to transport mobile homes. Tractor A vehicle designed primarily to pull a semi-trailer by means of a fi fth wheel mounted over the rear axle(s). Sometimes called a truck tractor or highway tractor to differentiate from it from a farm tractor. Tractor Trailer Tractor and semi-trailer combination. Transfer Case Used in all-wheel drive applications, power from the transmission is directed to the transfer case, which then transfers that power to both the front and rear axles. Transfer Dump A straight dump truck pulling a full dump trailer without hydraulics. The dump box of the trailer slides (transfers) into the empty dump bed of the power unit utilizing the hydraulics of the power unit to unload. Transmission Mechanism containing a number of gears that convert engine torque into useable power that can accommodate different vehicle loads and speeds. Tri-Axle - Tridem Truck, tractor or trailer with three axles grouped together. Trip Leasing Leasing a company s vehicle to another transportation provider for a single trip. Trip Recorder (On-Board Computer) Cab-mounted device which electronically or mechanically records data such as truck speed, engine rpm, idle time and other information useful to trucking management. Truck Vehicle which carries cargo in a body mounted to its chassis, rather than on a trailer towed by the vehicle. Tube Trailer A semi-trailer used to transport cryogenic gases. Turnpike Doubles A combination vehicle consisting of a tractor pulling two 40 to 53 foot semi-trailers. Turntable A circular platform mounted under the front of a full trailer or a jeep dolly to which an axle or axles are attached, allowing the axles to pivot in a turning maneuver. Twins (Twin Trailers) See Doubles. Twin Screw A truck or tractor with two rear axles, both driven by the engine. U ULEV Ultra-low emissions vehicle. ULSD Ultra-Low Sulfur Diesel fuel, containing less than 15 parts per million (p.p.m.) sulfur content. Upper Coupler Load bearing surface on the underside of the front of a semi-trailer. It rests on the fifth wheel of a tractor or dolly and has a downward-protruding kingpin which is captured by the locking jaws of the fi fth wheel. 14
Under-ride Guard A rear impact guard installed at the rear or under the rear of the cargo body of a truck or trailer so that when the vehicle is struck from the rear, it can limit the distance that the striking vehicle s front end slides under the rear of the truck or trailer. Most semi-trailers have what are known as ICC bumpers, but a hydraulic lift-gate at the rear of a box van can act as an under-ride guard. See ICC BUMPER. Universal Joint Also known as U-joint or yoke. The U-joint, found at both ends of the shaft assembly, allows the engine s power to fl ow freely to the rear drive axle even when a sudden change in the relative heights of the transmission and rear axle occurs, such as when the vehicle hits a bump. Upside Down The situation in which the amount owed exceeds the trade-in value. This is a common occurrence in the early years of a fi nance contract. V Van A cargo body style with a totally enclosed cargo area. Included are beverage vans, or bay vans, and sealed shipping containers mounted on a special bodiless chassis. Wheelbase The distance from center of front axle to center of rear axle, for a two axle vehicle, or front axle center to the midpoint between the rear tandem axle centers for a three axle vehicle. For a truck tractor and semi-trailer combination, wheelbase refers to from the center of the front tractor axle to the center of the rearmost trailer axle. Winch Truck A winch is a powered spool wound with cable. Winches are used to lift or to pull heavy objects. Winches vary in size from those on the front of small vehicles to heavy equipment which may weigh tons. Wrecker A truck designed for hoisting and towing disabled vehicles. Y Yard Jockey Person who operates a yard tractor. Yard Tractor (Yard Mule, Yard Goat, Yard Horse, Spotter) Special tractor used to move trailers short distances in a truck yard around a warehouse, distribution center, or terminal compound. Sometimes old, spare, or unroadworthy tractors are used. VIN (Vehicle Identification Number) Assigned by the manufacturer, this 17 digit number is unique to each vehicle and appears on the vehicle s registration and title. V-engine V-engines are named for the shape that their cylinders form when you look at the engine from either end. In the case of the V, the cylinder heads are offset from one another by less than 180 degrees, hence the V shape. W Walking Beam Suspension Type of truck and tractor rear suspension consisting of two beams, one at each side of the chassis, which pivot in the center and connect at the front to one axle of a tandem and at the rear to the other axle. Walking Floor Also known as a live bottom, a type of dump trailer with a conveyor belt or chain running down the center of the fl oor of the trailer to unload the cargo. 15