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How Much Do You Know About Special Rigs? Part I

When it comes to trucking, most of us think of the standard tractor and box trailer. Sure, there are some regional variations, such as those with dry vans and reefers, but there are so many more combinations than those we are most familiar with.

Today we are going to begin our three Part series on special rigs. A “special rig” is any combination vehicle that differs in any way from a dry freight or standard tractor-trailer with five axles and up to 18 wheels.

There are four primary types of special rigs in trucking today.

They include:

  • Multiple articulation vehicles;
  • Oversize vehicles;
  • High center-of-gravity vehicles;
  • Special cargo vehicles.

Let’s start with the first, and perhaps most commonly seen of special rigs.

Multiple Articulation Vehicles

Multiple articulation vehicles are also known as longer combination vehicles (LCVs). They have several joints or more than one point of the vehicle that is joined, while a typical tractor-trailer only has one joint, which can be found at the connection between the king pin and fifth wheel.

Multiple articulation vehicles come in various types of doubles and triples. Doubles consist of a tractor and two semi-trailers, with the second trailer converted to a full trailer using a converter gear – which is a set of fifth wheels with a fifth wheel, or converter dolly.

Here is an overview of the different types of doubles out there today:

  • A-train: The most common type, with a single drawbar;
  • B-train: Hooks up with two parallel drawbars;
  • C-train: The rear trailer cannot rotate at the hitch point.

While a standard tractor-trailer has one point of articulation, or joint, doubles have three. There are also several different setup types listed under the train categories.

They include:

  • Western doubles: A standard A-train with two equal length trailers of either dry van, tanker, flatbed or dump. They typically range from 24-31 feet and have an overall length of 60-75 feet.
  • Turnpike doubles: A turnpike double has longer trailers than a western double. They are also typically equipped with nine axles. They typically range from 35-48 feet with an overall length of 100 feet or more.
  • Rocky mountain doubles: A rocky mountain double is composed of a longer trailer in the front and a shorter trailer in the rear. In this setup the front trailer does require extra room for maneuvering. The front trailer is typically 40-53 feet while the rear is 26-29 feet. Overall length ranges around 80-100 feet.

The final cog in the multiple articulation wheel are triples. Triple trailers are made up of three semi-trailers, with the second and third converted to full trailers using converter gear, a drawbar and a pintle hook. Triples have three kingpin and two eye connections and have overall lengths of up to 100 feet.

Triple trailers definitely require truck drivers to exhibit more advanced operating skills. Due to their long length, additional time and space must be taken when making turns, stopping or performing other on- or off-road maneuvers. You will never want to back up connected to a triple trailer.

Before operating or hauling doubles or triples, you have to have a special endorsement on your CDL. You obtain this endorsement by passing a knowledge test. There are special driving and handling requirements that you must be aware of before getting behind the wheel of a double or a triple trailer.

Because of this, some states limit or prohibit the operation of doubles within state lines, depending on the weight and length of the setup involved. Always remember that you may need to obtain certain state permits before driving doubles or triples in certain states.

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