The double drop trailer (also known as a "lowboy" in some regional usage, though true lowboys are a distinct heavy-haul variant) is engineered to carry the tallest freight that can still move under its own height without an oversize permit. Two deck drops — one behind the gooseneck and one before the rear axles — create a lowered center well that sits just 18 to 24 inches above the pavement, roughly half the deck height of a standard flatbed. With the well deck that close to the ground, cargo up to approximately 11.5 ft tall can be transported within the federal 13 ft 6 in legal height limit. That extra clearance — about 3 feet more than a standard flatbed and 18 inches more than a step deck — makes the double drop the right equipment for freight that simply will not clear bridges and overpasses on any other open-deck trailer without a permit. The well deck length is typically 25–29 ft, which is substantially shorter than the overall trailer. This limits the footprint of what can sit in the well. Cargo longer than the well must extend onto the sloped front or rear ramp sections, which introduces load distribution and stability considerations. Extendable double drop trailers can stretch the well to accommodate longer equipment, though this triggers permit requirements in most states. Cargo securement follows FMCSA 49 CFR Part 393 with typical use of chains, binders, and blocking for heavy equipment. The low deck height means tie-down anchor points are close to the cargo center of gravity, which is an advantage for securement stability. Route planning for double drop loads requires attention to low-clearance obstacles, bridge weights, grade transitions at the origin and destination, and any railroad crossings that could cause well deck contact.
| Typical length | 48–53 ft overall; well (lower deck) approximately 25–29 ft usable |
| Typical width | 8.5 ft (102 in); extendable models available for wider loads with permits |
| Typical height | Well deck sits approximately 18–24 in above ground — allows cargo up to approximately 11.5 ft tall within the 13.5 ft legal height limit |
| Payload capacity | 40,000–45,000 lb (varies by axle configuration and trailer spec) |
New double drop trailers typically range from $45,000–$80,000 depending on spec, well length, and whether the unit is extendable. Specialty equipment carries a rate premium versus standard flatbed and step deck.
Typically up to approximately 11.5 ft, given a well deck height of about 18–24 inches above the ground and a maximum legal total height of 13 ft 6 in. Actual usable height depends on the specific trailer's well deck measurement — always verify with the carrier before booking.
The key difference is how cargo is loaded. On a double drop, cargo must be lifted onto the well deck by crane or placed from above. An RGN (Removable Gooseneck) has a detachable front section that lowers the deck to ground level, allowing cargo to drive on under its own power. For self-propelled equipment (excavators, dozers), RGN is required. For non-mobile cargo (transformers, machines), either type works if the well clears the height requirement.
Typically 25–29 ft, though this varies by manufacturer and model. Extendable double drop trailers can lengthen the well, but extensions require permits in most states. Confirm the exact well length with your carrier before booking machinery or equipment with a long footprint.
Not necessarily. If the cargo fits within legal height (13.5 ft), width (8.5 ft), and gross weight (80,000 lb) limits, no permit is required. Permits are triggered when any of those thresholds are exceeded. For very heavy equipment, axle weight distribution across the double drop's configuration may require a weight variance permit even when gross weight is under limit.
Technically yes, but it is rarely economical. Double drop trailers are more expensive to operate and the well deck geometry makes standard palletized or flat cargo loading awkward. Shippers typically book double drops only when step deck or flatbed height clearance is insufficient.