Just a guess but google says:
Truck and Bus Glossary
Quote:
A-Train
"A-TRAIN" - (Slang) a truck tractor pulling more than one trailer connected by "A" dollies
|
Like this:
Quote:
"B-Train"
"B-TRAIN" - (Slang) a truck tractor pulling two semi trailers where the second trailer sits on a fifth wheel that is permanently attached and extends off the rear of the lead trailer. Most commonly used on flatbeds or tank trailers. The "B"train is considered a more stable double trailers configuration.
|
More like this:
But that's just a guess