A double drop trailer, or lowboy trailer, is a specialized trailer that has several unique capabilities. A double drop is often referred to as an RGN, but more on that later. Its lower deck height allows the driver to haul taller commodities like equipment and machinery. We'll dive into all the specifics of this trailer type including dimensions, axle groups and weights, accessories, and more. A double drop trailer will certainly take an understanding of oversize and overweight loads as this trailer is geared for that market. Let's take a look at this specialized trailer and all its capabilities.
Types of Trailers & Dimensions
A Note About Dimensions
Dimensions can vary on trailers and state regulations. Be sure you understand the state requirements and trailer before hauling any load. DO NOT use any dimensions listed below as they are intended as averages and for general industry understanding.
Double Drop
Commodity Hauling
Like most open deck trailers, they can haul a wide range of commodities, but they are less likely to focus an use on general freight-all-kinds (FAK) that can be hauled on flatbed and step deck trailers. Because a double drop is a specialize trailer, they are used primarily for large equipment and machinery. The key advantage to this trailer is its lower deck height, although it has another unique capability. Most double drops have a removable gooseneck (RGN). This feature allows for the lower deck to separate from the front upper deck allowing for wheeled or tracked equipment to be driven onto the trailer.
Removable Gooseneck or RGN
When a driver deploys the removable goosneck, he can pull the tractor away allowing access to equipment being driven on the load. Once the load is on the bottom deck of the trailer, the driver backs up to the trailer and reattaches the gooseneck.
Double Drop Dimensions
There are all types of trailers that fall into the double drop or lowboy group. These dimensions can vary, so this is more of a generic list of dimensions on what you can likely expect. The driver is most qualified to determine what commodity dimensions will work on his trailer and skill level. Oversize and overweight loads can vary on trailer setup and have different requirements depending on the states being traveled.
Double Drop Length
In order to having the hauling capability of a double drop, you have to have the bottom deck as low as possible. The sacrifice for this height is a much reduced bottom deck length. Typically the more specialized the trailer the more it weighs reducing the commodity weight the equipment and legally haul without an overweight permit.
- Overall Length - The overall deck length is generally between 48' - 53' long. The overall deck length will help dictate the bottom deck length, but axle groups, specifically multi axles trailers, can affect overall and bottom deck lengths.
- Bottom Deck Length - This bottom deck is often referred to as the "well" of the trailer. A typical 5 axle double drop can expect around 29' in length.
- Upper decks - There are many setups here. A double drop or lowboy can have upper decks in the front and rear of the trailer. With that said, there are trailers that don't have any upper deck space to utilize or may only have one upper deck in the front or rear.
- Commodity Length - Discussing commodity length can encompass a lot of things. It's not as easy knowing the bottom deck length and that being the max commodity length. There are two terms that would be discussed and understand on any load when working with double drop trailers.
- Footprint - The commodity footprint refers to the length of the commodity that sits on the ground. Think of a tracked excavator that has a bucket arm attached. The tracked portions sits on the ground in its entirety.
- Overhang - The excavator arm extends over the ground allowing for the possibility for the arm to overhang the upper front or rear deck of the double drop.
- Overlength Loads - Over length loads can refer to an overall tractor, trailer, commodity dimension. Typically this is the measurement from the tractor front bumper to the rear trailer, if a stretch trailer is being used, or commodity, if there is overhang off the rear trailer. States vary on the lengths requirements and permit costs.
Double Drop Width
The width is fairly straight forward. Most open deck trailers are 8'6" (102") wide. This is the legal limit for commodity width as well, so it's one of the first dimensions to know and understand in the trucking industry.
- Trailer Width - Most open deck trailers are 8'6" (102"). Often the deck width is referred to as a "102" referring to the 102 inches dimension.
- Legal Commodity Width - The max legal commodity dimension is 8'6" (102"). Any load exceeding this limit is considered oversize and would require state permit.
- Overwidth Loads - If the commodity is over 8'6", a state oversize permit is going to be required. If the load gets too wide, about 12' wide or greater, then an oversize escort will be required as well. This is dependent on many factors.
- Outriggers - Some double drop trailers have what are called outriggers which allow to expand the width of the trailer enabling a larger platform surface for large wheeled or tracked equipment to set on the trailer. In other words the wheels of the equipment can be far enough apart that the trailer width of 8'6" is not enough to full support the wheels. There are three basic types of outriggers, but the all serve the same purpose.
- Pull Out
- Swing Out
- Attached.
Double Drop Height
As discussed above, dimensions can vary among double drop trailers. When discussing with a driver on the load, be sure you discuss commodity height. Overall height can vary due to driver's trailer height.
Important! Inches matter if a load becomes over height. Be sure you know your commodity height.
- Deck Height - The bottom deck or well of the trailer is typically 18"-24" off the ground. Because there can be up to 6 inches difference among trailers, don't assume a load will be legal or overheight. Always know the commodity height and tell the driver who will know their trailer's deck height.
- Transition Height - The height from the upper deck to lower deck. This can vary among trailers and differ between upper and rear decks. Suffice it to say, it's very important to understand the dimensions and commodity when discussing a load with the driver when these transition heights play an important role.
- Commodity Height - A double drop can haul a commodity height legally (without an oversize permit) typically between 11'6" and 12'. If the commodity exceeds the legal height limit, then permits and possible escorts (pole car) will be required.
- Oversize Height - States and routes can all vary when over-height permits are required. Overall height requirements will vary when a pole car and other escorts are required as well. All this means that over-height loads can quickly increase in cost.
Double Drop Weight
When hauling any load you should know the empty weight and commodity weight. Adding these two weight together will give you the overall weight of the load.
- Empty Weight - The combined weight of the tractor, trailer, fuel, and driver.
- Commodity Weight - The weight of the commodity to be transported.
- Overall Weight = Empty Weight + Commodity Weight
Although 80,000 lbs is the max gross legal weight allowed, the states actually break this down by weights on each axle group. This means that a load could exceed the legal axle group weight, but still be under 80,000 lbs gross.
- Empty Weight - As mentioned, several factors will determine the empty weight of the tractor trailer, but typically the empty weight is going to be around 38,000 to 40,000 lbs.
- Commodity Weight - A double drop can haul around 40,000 to 42,000 lbs before requiring an over-weight permit.
- Overweight Loads - When a load exceeds the overall or axle group weight limits, then an overweight permit is required. An overweight permit is generally more expensive than an oversize permit, but often an overweight permits will include any oversize permit requirements as well.
Accessories
There are many double drop accessories that can make a trailer more versatile. Some accessories are value added in that there are additional costs on the load. Tarping is an excellent example of an accessorial that requires more expense. Some of the accessories listed below are not equipment oriented, an accessorial could also be truck or driver provided, meaning a driver or truck has a license or expertise that not all drivers or trucks have and, therefore, provide a value add.
- Tarps - Open deck trailers, including double drops, haul commodities that are open to the weather, road debris, and wind (highway speeds too). A tarp can can help protect the commodity, but they aren't fool proof either. Tarps can rip or have holes and if a customer has sensitive commodities then further protection is required like crates, etc.
- RGN - Most double drop trailers have an RGN, but not all of them. Provides easy loading for wheeled or tracked equipment and vehicles.
- Outriggers - Extensions on the sides of the trailer that expand the trailer width in which to set or driver wide loads.
- Dunnage - Dunnage is typically wood blocking that allows for support or platform to set material on. Because dunnage can provide a wide variety of uses it is important to have an understanding of what is actually required for the load and this will help determine how much dunnage is needed.
- Stretch Trailer - A stretch double drop allows for the bottom deck to extend in length for hauling longer commodities. A stretch trailer may extend the lower deck up to 50'.
- TWIC Card - The "Transportation Worker Identification Credential" is a government provided card that allows a driver access to a secure areas of the nation's maritime facilities and vessels often called the ports.
- Canada - Not all carriers, equipment, and drivers are allowed travel into Canada.
