Doubles and triples are also known as Longer Combination Vehicles (LCV).
Attaching more than one trailer to a truck is known as hauling a double (two trailers) or triple (three trailers) and makes the resulting a longer combination vehicle (LCV).
This differs from hauling the standard 5-axle semi-trailers in that multiple will be coupled together and led by a single tractor.
The rules governing hauling multiple trailers differ from state to state and it is illegal to pull triple trailers in many states.
CDL drivers will be required to pass an exam to get their doubles-triples endorsement, and the doubles-triples endorsement will be indicated with a 'T' on a driver's CDL.
Double and triples refer to hauling multiple trailers coupled together. Typically, these are some combination of two sub-53-foot trailers that are joined together. These trailers are typically hauled to a central hub where they will be dropped off and broken apart to be hauled by others to their final destinations.
Length and weight limits may vary by state, and certain lengths of LCV's will require driving only on highways or turnpikes.
There are multiple benefits and considerations when it comes to doubles and triples, let's look at a few of each below.
More efficient: Hauling doubles and triples is more efficient as one tractor can haul multiple trailers at once. This ability is thought to help keep consumer prices low and is considered more environmentally friendly by Canadian truckers.
More money: Companies like that the increased efficiency can help their bottom line as well. For example, only one driver is able to do the work of two or three and saves the operator money in the process. Drivers also can count on an increased rate, though not always.
Can be an easier haul: One nice thing about hauling doubles and triples is that some of the manual labor is typically taken care of. This means that trailers can often be pre-loaded and are simply dropped off and exchanged at a hub. Drivers usually end the day at their home terminal.
Limited opportunities: The most common goods to be hauled using LCVs are agricultural and food products. This makes the demand for hauling LCVs more seasonal when compared to other types of freight.
Safety concerns: Not everyone is a fan of having doubles and triples on the road. For many truckers, it is a matter of perceived safety. This video does a good job highlighting some of the concerns that truckers have when it comes to safety:
Increased regulations: Hauling multiple trailers will further restrict further the routes and roads that are open to a driver. This is because doubles and triples often have a larger weight or length that can run over some jurisdiction's allowable maximums. This means that drivers will have to spend significantly more time and attention on routing when hauling doubles or triples.
Drivers will have to pass a knowledge exam to gain their LCV endorsement and gain the ability to haul doubles and triples. The exam is 25 questions in length and drivers are required to score 80% or above. The endorsement is good for the lifetime of the CDL.
The exam covers standard procedures for assembly and hookup of the units. This includes knowing things such as the proper placement of the heaviest trailer. Additionally, drivers will be expected to understand handling and stability characteristics including off-tracking, response to steering, sensory feedback, braking, oscillatory sway, rollover in steady turns, and yaw stability in steady turns.
Finally, drivers will be expected to be able to identify potential problems in traffic operations, including problems the motor vehicle creates for other motorists due to slower speeds on steep grades, longer passing times, the possibility of blocking the entry of other motor vehicles on freeways, splash and spray impacts, aerodynamic buffeting, view blockages, and lateral placement.
Warm up with CDL practice tests for doubles and triples here.
There is no road test required specifically for driving doubles or triples.
The main way LCVs are regulated is by the type of roads that they can use. Certain routes (mainly the Interstate Highway System and other specified non-interstate highways) are required to allow LCVs due to being part of the National Network. This is because of requirements spelled out in the Surface Transportation Assistance Act of 1982 (STAA). This act established minimum and maximum length restrictions on commercial motor vehicles (CMVs).
States are required to allow doubles in combinations of 28 feet each in length on the National Network—with the overall length of the trailer combination to be a maximum of 65 feet. Federal weight limits on the National Network are set at 80,000 lbs, and special permits will be required for hauling over 80,000 lbs on the NN.
Weight limits for doubles and triples are calculated on a weight-to-length basis, according to the number of axles, trailer configuration, and weight on each axle.
See Also: Bridge Formula Weights Calculator
Individual states cannot set their maximum CMV weight at lower than 80,000 lbs on the National Network. They can, however, specify their own requirements on their own roads outside of the National Network. Because of this, additional weight and length restrictions vary by state, so drivers will need to check state regulations when pulling LCVs. For example, certain states will only allow certain combinations on different routes within their state, outside of the National Network.
Each state may also require specific permits to haul doubles and triples through them. Drivers will need to plan their route accordingly and be aware of specific state regulations on their route.
To see an example of how different states can treat LCVs differently, check out how California and North Dakota deal with those hauling doubles or triples.
Spend time on safety checks: More trailers often mean a more thorough inspection process. And it may take a little bit longer to inspect multiple trailers and the coupling system but doing so is of the utmost importance. For a practical demonstration of what a safety check looks like for an LCV, check out this video of a FedEx Ground Doubles arrangement.
Operation is different: Due to the added length, there are some additional considerations to keep in mind when pulling doubles or triples. Drivers will need to know how to best manage their space to maintain safe stopping distances. This can be difficult with a variety of different vehicles mixed on the roads but allowing for more following distance and longer gaps in traffic before entering or crossing traffic.
Be wary of adverse conditions: Everything from a blizzard to a slippery mountain road can be enough to take even experienced doubles drivers off the road. That's why drivers need to be especially careful if they drive double and triple bottoms. LCVs have greater length and more dead axles to pull with their drive axles than other drivers. This means there is more chance for skids and loss of traction.
While all states allow the standard combination of two 28-foot semi-trailers, according to the Department of Energy, only 14 states and six state turnpikes currently allow longer combination LCVs. The routes that allow drivers to haul doubles and triples have not substantially changed since 1991.
States that allow LCVs on select routes include:
Please enjoy the following kernals of wisdom straight from real Trucking Truth forum members.
It's not hard at all. Especially if both trailers are pups. If you watch what happens in the mirror, when the first trailer straightens out behind you, it pulls the next trailer forward and away from the object you are attempting to miss. It was kinda cool watching that for the first time and then realizing what it was doing.
I suggest getting all your endorsements at the time of testing, since you never know what opportunity might come up…. Point being is that you don't know the future, so you should put yourself in the best possible position to accept any opportunity that comes down the pike.
[A] lot of freight is on a schedule. They can't wait for enough freight to load a 53' trailer. A 28' gets loaded faster. They only get unloaded if they reach their final destination or if it's coming from a terminal that doesn't sort freight. A terminal that only does p/d still had their pick-ups. They'll load those pick-ups into a 28' and send them to the closest hub to be sorted.
A CDL is required to drive any of the following vehicles:
A facility where trucking companies operate out of, or their "home base" if you will. A lot of major companies have multiple terminals around the country which usually consist of the main office building, a drop lot for trailers, and sometimes a repair shop and wash facilities.
A vehicle with two separate parts - the power unit (tractor) and the trailer. Tractor-trailers are considered combination vehicles.
A commercial motor vehicle is any vehicle used in commerce to transport passengers or property with either:
A department of the federal executive branch responsible for the national highways and for railroad and airline safety. It also manages Amtrak, the national railroad system, and the Coast Guard.
State and Federal DOT Officers are responsible for commercial vehicle enforcement. "The truck police" you could call them.
A CMV is a vehicle that is used as part of a business, is involved in interstate commerce, and may fit any of these descriptions:
Commercial trade, business, movement of goods or money, or transportation from one state to another, regulated by the Federal Department Of Transportation (DOT).
Refers to pulling two trailers at the same time, otherwise known as "pups" or "pup trailers" because they're only about 28 feet long. However there are some states that allow doubles that are each 48 feet in length.
The state agency that handles everything related to your driver's licences, including testing, issuance, transfers, and revocation.
Operating While Intoxicated