The lowboy trailer is built around a single engineering goal: get the deck as close to the ground as possible. By using a dropped well section — typically 18 to 24 inches above the road surface — between a raised gooseneck neck and a raised rear tail, a lowboy creates the maximum possible cargo height clearance under the legal 13 ft 6 in limit. A piece of equipment riding on a double-drop deck at 24 inches can be nearly 11 feet tall and still clear bridges. The same machine on a standard flatbed would require permits or be impractical to move. The well length — the actual low section — is typically 24 to 29 feet, but the trailer's overall footprint including the neck and tail runs 48 to 53 feet. The shorter well limits how long a single piece of equipment can be while still centering its weight over the axle group. For very long equipment, extended-neck configurations or multi-axle trailers are used. Payload capacity is where the lowboy truly distinguishes itself. A standard 3-axle lowboy handles 40,000 to 50,000 lb in the well. Adding axles — either fixed or removable jeep axles on the neck and boosters on the tail — extends legal payload to 80,000 lb and beyond. Superloads exceeding state legal limits require engineering analyses and special permits but the lowboy frame is capable of far higher loads with proper axle distribution. Every heavy haul move requires advance planning. State permit offices issue oversize and overweight permits on different schedules, with different route restrictions (curfews near cities, bridge weight limits, restricted roads). A cross-country lowboy move touching five states can require five separate permit applications, each with different lead times. The transport company's permit department manages this — shippers should provide accurate cargo dimensions and weights before quoting. The lowboy is not the same as an RGN (removable gooseneck). An RGN allows equipment to be driven directly onto the deck from the front after the neck is detached. A lowboy's neck is fixed — equipment must be loaded from the side using ramps or cranes. For most rubber-tired construction equipment, either works. For very wide tracked equipment with no side access, RGN is required.
| Typical length | 24–29 ft well (48–53 ft overall with neck and tail) |
| Typical width | 8.5 ft standard; up to 14 ft with superwide permits |
| Typical height | Deck height approximately 18–24 in above ground in the well; maximum legal cargo height 13 ft 6 in total |
| Payload capacity | 40,000–80,000 lb standard configuration; 100,000+ lb with additional axles and permits |
New lowboy trailers range from $60,000–$120,000+ depending on axle configuration and weight rating. Per-move rates reflect permit cost, pilot car fees, and route survey requirements — heavy haul is priced per-project, not per-mile.
The terms are often used interchangeably, but in practice a lowboy is engineered specifically for heavy haul — heavier frame rails, more axle positions, and higher payload ratings. A double-drop (or double-drop step-deck) may share a similar deck profile but is typically rated for lighter loads. For overweight permitted moves, verify the trailer's actual axle ratings and frame certification rather than relying on the name.
Federal bridge law limits gross vehicle weight to 80,000 lb on the Interstate system without a permit. With state overweight permits and additional axles, lowboys routinely operate at 100,000–150,000 lb on designated routes. True superloads (over 200,000 lb) require engineering studies, bridge analyses, and state-specific authorization — some moves require temporary road reinforcement.
In most cases, yes. Width over 12 ft typically requires one front escort; width over 14–16 ft often requires front and rear escorts. Unusual height or length may trigger additional requirements. Requirements differ by state — the permit application process clarifies what is required for each route segment.
Most lowboys use rear ramps (beavertail) that fold down to allow driven equipment to load from the rear. Side craning is also used for equipment that cannot be driven. Unlike an RGN, equipment cannot be driven on from the front. The driver and riggers position the equipment so its heaviest axle or component sits over the trailer's axle group to maximize legal payload.
Plan for at least 3–5 business days for straightforward single or two-state moves. Complex multi-state routes, loads requiring route surveys, or moves in states with slower permit offices may need 1–3 weeks of lead time. Emergency moves are possible but incur significant premium costs for expedited permitting and after-hours service.