Simplify Your Oversize/Overweight Loads

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  • Calculate Max Legal/Permitted Axle Weights
  • Understand Equipment Limits
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Flatbeds and Step-Decks — Workhorses of Oversize Load Hauling


Flatbed trailers are perhaps the most versatile hauling trailer available. The two most commonly available flatbeds are the standard flatbed trailer and the step-deck flatbed. 

Properly loaded, secured, and protected, a flatbed can transport almost any cargo. 

A standard flatbed trailer is 48 feet long and 8.5 feet wide, providing more than 400 square feet of surface to support a load. The top of the flatbed is typically 58 inches above the road surface.  In most states on most highways, the maximum height for a load is 13.5 feet from the road surface to the top of the load. That means the load on the truck that exceeds 8.5 feet above the deck is an oversize (or over dimension) load. 

Types of cargo carried by both regular flatbed and step-decks include: 

  • Construction Equipment, Bulldozers, Backhoes, etc.
  • Farm Equipment
  • Industrial Machinery (regular and oversize)
  • Military Equipment
  • Prefabricated Buildings
  • Concrete Culverts
  • Long Steel Pipes
  • Rolls of wire or flexible plumbing
  • Logs, Lumbar, Building Supplies
  • Other vehicles

Flatbed Versus Step-Deck

A step-deck (also referred to as “drop deck” or “open deck” trailers) is a flatbed that provides two hauling decks. The 10 to 13 shorter forward deck over the kingpin is a standard 58-60 in. height haul items up to 8.5 feet high without an oversize permit. The aft, 38 to 40 ft. long lower deck is only 3.5 ft. above the road surface. That means that the lower deck can carry a load a little more than 10 feet high without requiring any oversize permits in most states. 

Flatbeds and step beds are relatively common equipment, familiar to most drivers. This discussion does not include low-boy trailers that tend to be used for more specialized purposes.

Key Factors for Successfully Transporting Oversize Loads

The fact that flatbed trailers allow oversize loads to extend beyond the edges of the trailers makes them the go-to vehicles for over-dimensional loads—loads that are excessively wide, tall, or long. 

Flatbeds, both regular and step-down, regularly carry oversized loads that require over-dimensional permits as well as “Oversize Load” banners, flags marking the corners of the load, safety lighting at night, and possibly escort vehicles, depending on the size of the load and specific state requirements.

Oversize Loads

An oversize load is any load that exceeds the maximum legal width, height, and/or length permitted on state and provincial loads. First, the dimensions are not uniform across states, but, typically, the maximum width is 8.5 feet and the maximum height limit is 13.5 to 14.5 feet. 

The width of 8.5 feet is standard across most states, especially on major highways. There are instances where, on secondary roads, the maximum width is 8 feet.

This illustrates the first challenge. Assume a load measures 14 feet high, from the road surface to the top of the load. Is an oversize permit required? The answer is “it depends.” If the state you are hauling in has a height limit of 14.5 feet, then no oversize permit is required for height. But if you travel through a neighboring state where the height limit is 13.5, you will be required to apply for and obtain a permit for that state. 

The legal length of loads are typically 48 to 53 feet, and in some cases, the load may overhang the end of the trailer by some length, for example five feet, without being considered oversize for permitting purposes. Again, this varies from state to state (see  Oversize and Overweight Loads Defined).


Again, in most states, a load more than 16 feet wide, 16 feet tall, or 160 feet long is considered a “superload.” Increased safety requirements, and fees, for Superloads, include route surveys, specific highway routes, restricted travel times, and the number and types of escort vehicles. The permitting process typically takes more time, and the whole process takes more planning.

The fact is, however, that flatbed trucks are the most efficient, cost effective means of transporting oversize loads. 


Many loads do not exceed the dimensions of a routine load but may exceed legal weight limits. The limiting factor for weights is the number and configuration of the axels of the truck. A typical eighteen-wheeler has a maximum legal weight of 80,000 pounds. (combined weight of the tractor trailer and the load), with the weight distributed evenly over the axels and axel groups. A properly loaded typical tractor-trailer at maximum weight will have 12,000 pounds on the front, steer axel, and a maximum of 34,000 pounds on each axel pair.  Note that if weighed, it is possible for a truck to be under the maximum 80,000 pounds weight and still be overweight on one set of axels, and subject to fines. Some trailers are equipped with axels that can be repositioned under the trailer to redistribute the load. The weight of the load must be properly distributed (see  Axel Weight Limits Calculator). 

Trucks may carry loads well in excess of 80,000 pounds on trucks equipped with added axels. However, any load in excess of 80,000 pounds is an overweight load, and an operator, as with over dimensional loads, must obtain a permit to transport the overweight load. Fees for overweight loads increase as the weight increases—and the fees vary from state to state.


The first step in the permitting process is to determine if a permit is necessary, and if required, determining the specific requirements of the permit. First, obtain accurate dimensions and weights, along with the planned route of travel.

As mentioned, not all states use the same dimensions to determine when a permit is required, and the details of the permit may vary from state to state. Flatbed operators are likely to eventually find themselves hauling an oversize load. 

If you or your company frequently transports oversize/overweight loads, the permitting process may become routine, but it does require a staff knowledgeable of the permitting process. If oversize loads are only an occasional part of your business, obtaining permits becomes an added, time-consuming chore. In either case, it may be worthwhile to use the services of an agency experienced in obtaining permits and making arrangements for other requirements such as escort services.  Of course, all oversize loads require that the trucks be equipped with “Wide Load” banners and other safety equipment as determined by each state.


Proper loading of flatbeds is critical. The key requirements are load stability and weight distribution. If the load consists of mixed freight, it is important that heavier items are loaded on the deck, and lighter items above since this will improve the stability of the load. Weight distribution, as indicated above, is important to ensure that the load on an axel or set of axels is not overweight. 

The Federal Motor Carrier Safety Administration (FMCSA) that regulates the U.S. trucking industry, also establishes rules for securing cargo. According to the FMCSA, the rules are necessary reduce the number of accidents caused by cargo shifting on…or falling from, commercial motor vehicles.

In general, the FMCSA requires that cargo be firmly secured by structures of sufficient strength such as tie-downs, chains, etc.

A variety of tie-down and restraint systems are available including, ropes, nets, chains, straps and webs among others. The type of restraint to be used depends on the type of load and the vehicle. 

Cargo that is likely to roll—i.e., vehicles (trucks, farm machinery, construction or quarry vehicles, etc.), rolls of wire, large pipes and culverts, etc., must be secured and held in place by wedges, chocks, or other means that that will prevent rolling and that will not come unfastened or loose while the vehicle is in transit. Chains must be added to prevent any chance of the load shifting.  

Building materials such as brick or blocks should be secured to pallets, and the pallets securely secured to the to prevent any possible movement fore and aft as well as side-to-side. Straps are best used for bulk commodities such as loads of lumber, pallets of building materials, etc.

If a load must be covered to protect it from wind or weather, the use of heavy tarps or netting is recommended. Of course, these covers must also be secured so that they are held firmly against the load. If tarps or netting can move in the wind of travel, they will rapidly wear, tear, and become a hazard of their own. 

There are specific strength requirements for tie-down straps and chains, based on the type of load, as well as the number and position of straps or chains to safely secure a load.

In summary, each load must be secured so that the cargo is not damaged but is securely restrained during transit.

Other Considerations

Flatbed drivers often find themselves picking up a load away from a depot—such as at a work or manufacturing site—and the loading may be done by personnel who may not be familiar with proper loading. In these situations, the driver may need to determine where various parts of the load should be placed on the trailer and direct the loading process. 

It is good practice inspect the load and trailer after it is loaded. If, for example, you are hauling a loader from a rock quarry, check the load for any loose gravel that may have fallen onto the deck. Loose gravel can eventually fall off the trailer resulting in damage to other vehicles—even possible accidents and injuries. In any case, check for loose items such as tools, hardware, loose straps, or sections of unused rope lying loose on the deck or on the load.


It makes sense—open decks are ideal for bulk products such as lumber, brick, wire coils, pallet loads that benefit from being loaded from the side of the trailer, as well as vehicles of all descriptions. 

Flatbeds, both standard and step-down types are used for the same types of hauling. Each configuration offers advantages and disadvantages, and their applications complement each other.  The standard flatbed can handle longer loads more easily, while the step-down can carry taller items without requiring an oversize permit. In summary, flatbed trailers are one of the most practical, versatile, and widely used trailers in the trucking industry.

And, flatbeds really provide the only routine transportation solution for over-dimensional loads that will not fit in a van or enclosed trailer.