Get your A B C’s Straight

Ever wonder what the difference between A Trains and B Trains were? Did you even know about the existence of C Trains? This article explains the different ways that two trailers are hooked to one another in North America. When you refer to a set of trailers as A, B or C trains you are really referring to the type of connection between the two.

A Train Semi Truck Trailers


This type of semi truck is connected by a dolly that is hooked up to a pintle hook on the rear of the forward trailer. The dolly has one or two axles, and it is licensed as a separate trailer.
Single axle A Trains are used extensively by the LTL industry. Companies like Estes, UPS, and Con-way use them to run between terminals, and will break up the trains for final delivery. Double axle A trains are used as well, but more often for Long Combination Vehicles, to put two 48’ or 53’ trailers together. A Trains are mostly used for pulling Van (enclosed) trailers.

B-Train Semi Truck Trailers


B-Trains are a truck-trailer combination where the axles of the lead trailer stick out and a fifth wheel is mounted on the lead trailer.
These combinations are used sometimes by LTL carriers, where the axles of the lead trailer slide from underneath the lead trailer so it can back into a door just like a regular trailer. Food service companies like Sysco systems also this type of trailer as well to extend their distribution network. A set of two can be pulled, usually overnight, to a city within 500 miles of the distribution center. Then, the trailers broken up and are taken by two fresh drivers for deliveries to restaurants and their other customers.
The B –Train combination is also very popular for hauling flatbed, bulk and liquid goods in Canada and some US states. Because these types of operations usually don’t require backing up into a dock, drivers will generally only drive forward, making it easier. However, most drivers that pull these on a regular basis can back them up fairly well, even into a dock or around a corner. The 8 axle, 63,500 kg B Train is a standard across Canada.

C-Train Semi Truck Trailers


C-Trains are the rarest of the double trailer combinations. Like an A-Train, the lead trailer pulls a dolly that the second trailer sits on. However, instead of one pintle hook, there are two. This removes one of the points of articulation from the unit, and makes the second trailer much more stable. However, it also makes it a lot harder to hook the dolly to the lead trailer, and the tires on the dolly will wear much quicker from going around corners.
I am only aware of C-Trains operating in Western Canada, pulling long combination vehicles, not shorter double trailers.

5 thoughts on “Get your A B C’s Straight”

  1. D- trains are also a thing. But i don’t think they have ever been used and mostly exsist on paper!

  2. How do C-trains steer? Seems like the dual pull bars would make for an extremely rigid wheelbase by comparison.

  3. I work with trains that the dolly is a part of the rear trailer and is attached on a bearing plate, it is unattachable. What would that be considered?

  4. Yes, it is intended to make the dolly rigid with the lead trailer. The dolly will skid around the back of the trailer and it will have the effect of extended the ‘real’ wheelbase of the lead trailer.

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