The single most important number in choosing a heavy-haul trailer is deck height — because total height (deck + cargo) has to clear bridges. The legal ceiling is generally 13'6". So the taller your cargo, the lower the deck you need to stay legal and avoid permits. That one idea explains the whole flatbed → step deck → RGN ladder.
Flatbed
A standard flatbed has a deck about 5 feet off the ground and runs 48–53 feet long, hauling up to roughly 48,000 lbs.
- Best for: cargo up to about 8'6" tall (5' deck + 8'6" load ≈ 13'6").
- Loads: building materials, steel, machinery that is heavy but not tall, palletized freight.
- Why pick it: cheapest specialized option, easy to load from any side or by crane.
Step deck (drop deck)
A step deck drops to a lower main deck around 3'6" off the ground, buying you height without a permit.
- Best for: cargo up to about 10 feet tall.
- Loads: taller machinery, equipment that would push a flatbed over height, anything you want to ramp on.
- Why pick it: ramps allow drive-on/roll-on loading; more legal height than a flatbed for a small cost bump.
RGN / lowboy
A removable gooseneck (RGN), or lowboy, has the lowest deck — roughly 18 to 24 inches — and the front detaches into a ramp so equipment can drive right on.
- Best for: the tallest cargo (around 11'6"+) and the heaviest loads.
- Loads: excavators, dozers, cranes, large industrial machinery, anything self-propelled.
- Why pick it: lowest deck = most height clearance; add axles (3, 4, or more) to legally carry very heavy loads.
Quick selector
Under ~8'6" tall, not super heavy? Flatbed.
Up to ~10' tall? Step deck.
Over ~10' tall, very heavy, or drives on its own? RGN / multi-axle lowboy.
Beyond the big three
For extreme loads there are double-drop and stretch trailers for very long cargo, multi-axle and perimeter trailers for the heaviest weights, and Schnabel-type rigs for true superloads. If your load needs one of those, it almost certainly needs oversize permits and escorts too.
Not sure which deck your load needs? That is our job to figure out. See heavy haul, check what it costs, or just send us the dimensions and we'll spec the right trailer.