Shippers researching open-deck trucking usually land on the same question: flatbed or step deck? Both trailer types exist to move the same category of freight — cargo too tall, too heavy, or too oddly shaped to fit inside a dry van or reefer — but they solve that problem differently. The deciding factor almost always comes down to deck height and how much vertical clearance the freight needs to stay within legal road limits. This page breaks down what each trailer is, how they differ, and how to figure out which one a given shipment actually needs.
What Is a Flatbed Trailer?
A standard flatbed is a single flat, level deck running the full length of the trailer with no sides, roof, or tiered levels. Most flatbeds run 48′ to 53′ long and 8.5′ wide, with the deck sitting roughly 60 inches (about 5′) off the ground.[1] Because the deck is flat and open on all sides, freight is typically loaded from the top or side with a forklift or crane, which makes flatbeds well suited to crated machinery, structural steel, building materials, palletized goods, and other cargo that doesn’t need to be driven on. Flatbeds are also the most common and most widely available open-deck trailer type, which usually means more capacity and more scheduling flexibility for standard-height loads.
What Is a Step Deck (Drop Deck) Trailer?
A step deck — also called a drop deck — has two deck levels: a short upper deck near the kingpin and a longer, lower rear deck that “steps down” after the trailer’s wheels. That lower deck typically sits around 42 inches (3’6″) off the ground, roughly 18 inches lower than a standard flatbed deck, though low-profile and super low-profile step decks can bring that down further, in some cases to 30 inches or less with smaller tires.[2] The lower deck exists specifically to buy back vertical clearance: because most of the freight rides on the lower section instead of the higher flatbed deck, taller cargo can be hauled while still staying under the legal height limit. Step decks are the go-to choice for tall machinery, construction and agricultural equipment, and anything else that would push a flatbed load over the height limit. Many step decks also come with rear ramps (a beavertail-style design), which lets self-propelled or wheeled equipment drive on and off under its own power instead of being craned or forklifted into place.[3]
Key Differences at a Glance
- Deck height: Flatbed deck sits about 60″ (5′) off the ground; step deck’s lower rear deck sits about 42″ (3’6″), with low-profile versions lower still.[1][2]
- Usable cargo height before hitting the legal limit: With a 13’6″ federal legal height ceiling on most roads, a flatbed load generally tops out around 8’6″ of stackable cargo height, while a step deck’s lower deck allows roughly 10′ of cargo height before running into the same limit.[2][4]
- Loading method: Flatbeds are almost always loaded from the top or side by forklift or crane. Step decks can be loaded the same way, or, when equipped with ramps, driven onto directly by self-propelled or wheeled equipment.[3]
- Typical freight: Flatbeds commonly haul building materials, structural steel, machinery, and palletized oversize goods. Step decks commonly haul taller construction and agricultural equipment, tall crated machinery, and anything that would exceed the legal height limit on a standard flatbed.
- Ramps for wheeled/self-propelled equipment: Not standard on every flatbed or step deck — but step decks are far more commonly configured with rear ramps because their lower deck height keeps the ramp angle manageable for driving equipment on and off.[3]
How to Decide Which Trailer You Need
The federal legal height limit for vehicles on most U.S. highways is 13’6″ (13 feet, 6 inches), a standard that traces back to the Surface Transportation Assistance Act of 1982; a small number of states allow slightly more on select routes, and some allow less on others.[4] Start there: add the height of the freight itself to the deck height it would ride on. If that total would exceed 13’6″ on a standard flatbed, a step deck (or, for taller loads still, a double drop/RGN trailer) is likely required to keep the shipment legal without a special permit. If the equipment is self-propelled or has wheels and needs to be driven on rather than lifted into place, a step deck’s lower deck angle usually makes for a safer, more manageable ramp incline.[3] If the freight is standard height, sits on a pallet or in a crate, and will be loaded by forklift or crane, a flatbed is usually sufficient and, because flatbeds are more widely available than step decks, often easier to schedule.
Permits and Legal Limits
There is no single federal height limit written into law for every road in the country — height limits are set state by state, with most states adopting 13’6″ as their standard and a handful allowing up to 14′ on certain routes.[4] That means a load that’s legal in one state can require a permit in the next. Because of this variation, any load that comes close to 13’6″ total height, regardless of which trailer it rides on, should be reviewed for state-specific permit requirements before a truck is dispatched. Great Western Transportation checks height, width, weight, and route against the applicable state limits and can confirm whether a load needs a permit before it moves, for both flatbed and step deck shipments.
How Great Western Helps You Choose
Great Western Transportation reviews the exact dimensions, weight, and loading method of a shipment before recommending flatbed, step deck, or, for taller loads, double drop or RGN equipment. Accurate dimensions matter more than anything else in that decision: if the height, width, or weight reported at booking is off, the wrong trailer type can be dispatched, or a required permit can be missed entirely, which leads to delays or a truck that has to be turned around. Every driver and truck is vetted for proper insurance, strong safety ratings, and a clean compliance record before being matched to a shipment. Great Western does not maintain a local terminal or fleet; shipments are coordinated through qualified, vetted carrier partners matched to the specific load, with our team available by phone throughout the process to answer questions and adjust plans as needed.
Frequently Asked Questions
Can a flatbed carry the same freight as a step deck?
Sometimes. If the freight’s total height on a standard flatbed deck stays within the legal limit, a flatbed can usually handle it. Once the combined height of the deck and the freight would exceed 13’6″, a step deck’s lower deck is typically needed to keep the load legal.[4]
Do step decks need ramps?
Not always. Ramps are only necessary when equipment is self-propelled or wheeled and needs to drive on and off the trailer under its own power. Freight that’s craned or forklifted into place doesn’t require ramps, even on a step deck.[3]
Which trailer is more available?
Standard flatbeds are the more common open-deck trailer type on the road, which generally means more scheduling flexibility. Step decks are less common and may take more lead time to source, particularly low-profile configurations.
Does GWTrans provide both flatbed and step deck trailers?
Yes. Great Western Transportation coordinates both flatbed and step deck shipments — along with double drop and RGN trailers for taller or heavier loads — through vetted carrier partners matched to the specific freight and dimensions.
What happens if I’m not sure which trailer I need?
That’s normal, and it’s part of what Great Western reviews before booking. Provide exact dimensions, weight, and how the freight will be loaded, and our team will confirm the right trailer type before a truck is dispatched.
Sources
- Standard flatbed trailer dimensions and deck height (~60″, 48′-53′ length, 8.5′ width) — Ryan Transportation, Standard Flatbed Dimensions
- Step deck (drop deck) lower deck height (~42″, low-profile variants lower) and usable cargo height — Ryan Transportation, Step Deck (Single-Drop) Trailer Dimensions and Uses and VeriTread, Step Deck Trailer Dimension, Weight, & Load Capacity
- Step deck ramp (beavertail) loading of self-propelled equipment — O Trucking, How to Load a Step Deck Trailer
- Federal and state legal height limits, Surface Transportation Assistance Act of 1982, 13’6″ standard — Federal Highway Administration, Federal Size Regulations for Commercial Motor Vehicles
Not sure whether your shipment needs a flatbed or a step deck? Contact Great Western Transportation with your freight’s dimensions, weight, and loading method, and our team will confirm the right trailer before a truck is dispatched.
Great Western Transportation
5000 Pleasanton Ave Ste 145, Pleasanton, CA 94566
Call Toll Free: 1-800-972-8484
