Heavy Haul Glossary

If you're new to oversize, the vocabulary is dense. Here are the 60+ terms heavy-haul dispatchers, drivers, and pilot car operators use every day — defined in plain English, ordered roughly by category and then alphabetically.

Trailers & equipment

RGN (Removable Goose Neck): A trailer where the front (gooseneck) section disconnects from the cargo deck, allowing the deck to drop to the ground for direct drive-on loading. Standard for construction equipment, anything that can drive itself onto the trailer.
Lowboy: A trailer with a very low cargo deck (typically 18–24" off the ground), used to haul tall loads while staying under height limits. Often used interchangeably with RGN in casual speech, though strictly they're different trailers.
Double drop: A trailer with two height drops in the deck (high at the gooseneck, lower in the middle "well", high again over the rear axles), giving a low well section for tall cargo without removable goosenecks.
Step deck (drop deck): A trailer with one height drop, giving a higher front section and a lower rear deck. Cheaper and simpler than a double drop; common for flatbed loads.
Flatbed: A trailer with a single flat deck, no drop sections. Standard for legal-height loads.
Jeep (jeep dolly): An additional axle group placed between the tractor and the trailer to distribute weight. Used to bring a heavy load into Bridge Formula B compliance.
Booster (booster axle): An additional axle group placed at the rear of the trailer. Same function as a jeep but at the back. Common to add a booster + jeep on heavy loads to spread weight across more axles.
Stinger steered trailer: A trailer where the rearmost axle is steerable, allowing tighter turns with extreme overall lengths (e.g., auto transporters, log trailers).
Dolly: A small wheeled platform connected between tractor and trailer or between two trailers, providing additional axle support and steering articulation. Used in oversize moves to distribute weight or enable tighter maneuvering.
Schnabel car: A specialized trailer for hauling extremely heavy or oversized loads where the load itself becomes a structural part of the trailer (load suspended between two trailer ends). Used for transformers, generators, and pressure vessels.

Dimensions & weight

Oversize (OS): A load exceeding federal or state legal dimension limits in any of width, height, or length. The federal legal-without-permit width is 8'6" (102"); height is 13'6" (most states allow 14'); length depends on configuration.
Overweight (OW): A load exceeding federal or state gross weight limits. The federal Interstate cap is 80,000 lb gross; single axle 20,000 lb; tandem 34,000 lb.
OSOW: Oversize and overweight — the combined term used by state DOT permit offices.
Superload: A load exceeding specific state-defined thresholds that trigger additional permit conditions, engineering review, and often state police escort. Thresholds vary: Arizona triggers superload at >14' wide, >16' high, >120' long, or >250,000 lb GVW; other states use different numbers.
GVW (Gross Vehicle Weight): The total weight of the loaded vehicle including tractor, trailer, cargo, fuel, driver, equipment — everything that crosses a scale.
Gross: Shorthand for GVW. "What's the gross on this load?" = "What's the total loaded weight?"
Tare: The empty weight of the tractor and trailer (no cargo). Gross minus tare = payload.
Payload: The weight of the cargo only, without tractor/trailer/fuel/driver. Payload = gross − tare.
Overhang: The portion of cargo extending beyond the front or rear of the trailer deck. Many states trigger additional escort requirements when overhang exceeds 10–25 feet, independent of overall length.
Axle spacing: The distance between consecutive axles on a tractor or trailer. Wider axle spacing allows higher weight per Bridge Formula B.
Kingpin: The forward connection point on the trailer that locks into the tractor's fifth wheel. The "kingpin to rear axle" measurement matters for California's 40-foot kingpin limit and similar state rules.

Permits

OSOW permit: State-issued authorization to move a load exceeding legal dimensions or weight on that state's highways. Required separately in each state the load traverses.
Single trip permit: A permit authorizing one specific move from origin to destination. Most permits are single-trip; they expire on delivery or after a specific number of days (typically 4–30).
Annual permit (blanket permit): A permit covering multiple moves of a specified dimension/weight envelope for a year. Cheaper per-move than single-trip but limited to predictable loads.
Envelope permit: A permit covering moves within a defined dimension envelope (e.g., up to 14'W x 16'H x 120'L x 250,000 lb in AZ). Different from a per-load permit; the load just has to fit inside the envelope.
Continuous travel: The ability to move 24/7 without time-of-day restrictions. Loads below specific dimension thresholds qualify in most states; above the thresholds, movement is daylight-only or restricted to specific hours.
Class C permit: State-specific permit class for non-standard moves requiring case-by-case engineering review. Arizona's term; other states use different naming.
Rate confirmation (rate con): The contract between broker and carrier confirming the agreed rate for a load. Standard freight industry term, used in heavy haul same as everywhere else.

Escorts & pilot cars

Pilot car (escort vehicle): A passenger vehicle or light truck that accompanies the oversize load, warning other traffic and clearing intersections. Required by every state above certain dimension thresholds.
Lead pilot (front escort): A pilot car running ahead of the load, scouting for low clearances, narrow lanes, and oncoming wide loads. Required when width or height exceeds the state's lead-pilot threshold.
Chase pilot (rear escort): A pilot car running behind the load, blocking traffic from passing during turns and warning following vehicles. Required at the state's chase-pilot threshold (typically 14' wide on 4-lane highways).
Height pole: A vertical pole mounted on the lead pilot car, set to slightly above the load's height. The pole strikes overhead obstructions (signs, wires, bridges) before the load does. Required by most states when load height exceeds 14'–15'.
Police escort (LE escort): A state trooper, county sheriff, or local police escort in a marked vehicle. Required for very wide loads (typically >16') or as a state-specific condition. Pay rate set by the state; billed back to the carrier.
OVERSIZE LOAD sign: A retractable yellow sign with 6" black letters, mounted on the front and rear of the load and each pilot car. Required when any single dimension exceeds legal limits.
Amber lights (rotating beacons): Rotating or flashing amber/yellow lights on the pilot car roof, used to draw attention to the convoy. Required by most state escort rules.

Routing & route surveys

Route survey: A physical or documented inspection of the planned route, identifying overhead clearances, bridge weight ratings, turning radius constraints, and traffic considerations. Required by most states for loads above specific height (often 14'6") or weight thresholds.
BFG (Bridge Formula Gross): The maximum gross weight allowed on a group of consecutive axles under the federal Bridge Formula B. See the Bridge Formula B calculator for the math.
Kingpin-to-rear-axle (KPRA): The measurement from the kingpin to the centerline of the rearmost trailer axle. California limits this to 40' for most trailers; other states have similar rules.
Vertical clearance: The minimum height of any obstruction (bridge, overpass, traffic signal) along the route. Critical when the load is taller than 14'6" — most US Interstate overpasses are 16' minimum but state and local roads vary.
Reasonable access: The principle that a permit must allow the truck to reach a terminal or loading site within a reasonable distance off the permitted route — typically one road mile.

Regulatory & agencies

FHWA (Federal Highway Administration): The federal agency that sets federal-aid highway standards, including the federal weight and width limits codified in 23 CFR Part 658 (which includes Bridge Formula B).
DOT (state DOT): The state-level department of transportation responsible for issuing OSOW permits. Each state has its own permit process, fee schedule, and conditions.
FMCSA (Federal Motor Carrier Safety Administration): The federal agency overseeing commercial motor carrier safety, including USDOT registration, MC#/MX# operating authority, driver HOS rules, and the SAFER database for carrier lookups.
SAFER (Safety and Fitness Electronic Records): The public FMCSA database where you look up carriers by MC# or USDOT#. Shows operating authority status, safety ratings, insurance on file, and inspection history.
USDOT number: The carrier's federal identifier issued by FMCSA. Different from MC# (operating authority number) but both are tracked on the SAFER lookup.
23 CFR Part 658: The federal regulation defining Interstate weight and width limits — including the 80,000 lb cap, the 8'6" width cap, single/tandem axle caps, and Bridge Formula B.

Operations

Dispatch: The act of assigning a load to a tractor + driver + trailer combination. Also the role/department doing the assigning.
BOL (Bill of Lading): The legal document evidencing the contract of carriage between shipper and carrier. Signed at pickup, again at delivery.
POD (Proof of Delivery): The signed BOL or other documentation evidencing the load was delivered. Required for invoicing.
Detention: Time a tractor + driver is held at a pickup or delivery beyond the agreed "free time" (typically 2 hours). Detention is billable per hour to the customer; common rate is $75–$100/hour.
Layover: Compensation for a driver and tractor sitting idle for a full day (typically 24 hours) due to customer delay. Different from detention; layover is daily, detention is hourly.
FSC (Fuel Surcharge): A variable per-mile or per-load charge that floats with diesel prices. Common reference is the weekly DOE diesel index — the FSC increases when fuel prices rise.
IFTA (International Fuel Tax Agreement): The agreement among US states and Canadian provinces under which a single fuel tax license covers all member jurisdictions. Quarterly reporting required.
ELD (Electronic Logging Device): The federally mandated device that records driver hours of service (HOS). Replaces paper logs. Samsara, Motive, and Geotab are common ELD providers.
HOS (Hours of Service): FMCSA rules governing how many hours a commercial driver can drive and work in a day or week. 11-hour daily drive max, 14-hour daily on-duty max, 60/70-hour weekly limits.
Factoring: Selling the carrier's invoice (typically at a 1.5–3% discount) to a factoring company in exchange for immediate payment. Common in small-carrier cash flow management.

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Last updated: 2026-06-05. Glossary maintained continuously. Spot a missing or unclear term? Email [email protected] — we'll add or revise within 48 hours.