If you are aiming to work for major LTL carriers like FedEx, UPS, or Old Dominion, obtaining your Doubles and Triples Endorsement is non-negotiable. This "T" endorsement allows Class A drivers to pull two or three trailers simultaneously. While it significantly increases your earning potential, it also demands a higher level of skill and knowledge than pulling a standard 53-foot van.
The physics of pulling multiple trailers are unforgiving. Unlike a standard combination vehicle, doubles and triples are highly susceptible to the "crack-the-whip" effect and rollover risks. This guide will break down the critical concepts you need to master to pass the written exam and drive safely.
A significant portion of the Doubles and Triples Endorsement exam focuses on the "Converter Dolly." This is the coupling device of one or two axles and a fifth wheel that allows you to couple a second or third semitrailer to the rear of a tractor-trailer combination.
You must understand that converter dollies have their own air tanks. Why? because they need to supply air to the brakes of the rear trailer. During your pre-trip inspection, you must check the Pintle Hook (on the lead trailer) and the Eye (on the dolly) for cracks or excessive wear. Unlike a standard fifth wheel connection, this connection point has more "play" and is a critical failure point if not inspected correctly.
This is where 60% of students fail their Doubles and Triples Endorsement test. You must understand which valves to open and which to close. If you get this wrong, the rear trailer brakes won't release, or worse, they won't apply when you need them.
| Location | Shut-off Valve Status |
|---|---|
| Rear of Front Trailer | OPEN (To let air back) |
| Rear of Dolly | OPEN (To let air to rear trailer) |
| Rear of Last Trailer | CLOSED (To hold pressure) |
Drivers call doubles "Wiggle Wagons" for a reason. They require a much smoother driving style. You must look further ahead than usual—at least 12-15 seconds. You also need to manage your space differently. Doubles take longer to stop empty than fully loaded because the stiff suspension and lack of weight cause tires to bounce and lock up.
Also, remember that you cannot back up doubles or triples. If you pull into a spot where you get stuck, you cannot reverse out without uncoupling everything. Planning your route and parking is not optional; it's survival.
A: No. In most states, the Doubles and Triples Endorsement is a written knowledge test only (usually 20 questions). There is no road test required, although your employer will likely require a road test.
A: Much more than a standard truck. Allow 1 second for every 10 feet of vehicle length at speeds under 40 mph. Add 1 second if going over 40 mph.
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