Advice: Do you know your A from your B?

Revolutionary trailer developments pioneered by Byford Equipment are known as A-Doubles.

This description should immediately make you see an image of a prime mover pulling a semi-trailer, with a drawbar trailer behind that.

However, most transport people I checked with didn’t get that instant picture. Why not? It’s because there’s confusion in this wide brown land of different combination vehicles, and most of it centres on the letters ‘A’ and ‘B’.

It’s not uncommon for an operator to say: “I just dropped the B-trailer and I’m going to deliver some stuff out of the A-trailer”.

He’s talking about a B-Double, of course.

We all know what he means, but his use of ‘A’ in referring to the lead trailer is wrong.
It’s wrong because a B-Double can’t have an ‘A’ trailer! It’s an accepted worldwide convention among truck engineers and road rule legislators that an A-type trailer is one with a drawbar coupling.

It’s another convention that dollies don’t count as a separate trailer, being part of the A-trailer coupling system, despite the fact that they’re fitted with turntables or fifth wheels.
A B-type trailer is one with a fifth-wheel coupling, be it a turntable or a greased plate. A B-Double gets its name from the fact that it has two trailers, both being B-types.

Originally, in Canada, where the B-Double concept began, it’s known as a B-Train, but the name was changed in Australia, because pollies were concerned about ‘selling’ the idea of small road trains operating in metro electorates. There’s more on this topic a little later in this story.

A Type One double road train has a B-coupled trailer pulling an A-coupled trailer and a Type Two triple road train has a B-coupled trailer pulling two A-coupled trailers. Getting confused? It gets worse.

In Europe and the USA, where combination types are pretty limited the ‘A’ and ‘B’ types are well understood, but here, in the home of the road train, it’s becoming more confusing by the week, it seems. A B-Triple is easy enough to figure out, because it’s an ordinary B-Double with a second ‘lead’ trailer slotted in.

Next is the AB-Triple that consists of a semi-trailer combination pulling a B-Double, via a drawbar-coupled dolly. Then there’s the ABB-Quad, where a semi-trailer is pulling a drawbar-coupled dolly, with a B-Triple behind it.

Another increasingly popular configuration is a pair of B-Doubles formed into a four-trailer road train. No, it’s not a B-Quad or a Double B-Double; it’s a BAB-Quad.

But what do you call a double road train that’s pulling a B-Double; a typical road train tanker rig in the NT and WA? It’s an AB-Quad.

Yet another useful combo is a B-Double pulling two trailers: it’s a BA-Quad. However, does the use of the term ‘quad’ cause confusion in the minds of those who run ‘quad dogs’ (four-axle dog trailers) and semi-trailers with quad axles?

Complicating the situation even more is the renaming of what are obviously Type One road trains as ‘A-Doubles’. This is happening increasingly as Performance Based Standards (PBS) approvals are granted for Type One road trains to operate on major routes in metropolitan areas.

These so-called A-Doubles are mainly operating as tankers and container haulers, pulling two full-sized semi-trailers on multi-lane roads through heavily trafficked areas and, so far, there hasn’t been any major outcry. It’s possible most car drivers think they’re B-Doubles.

After all, with many road transport professionals confused about their As and Bs, it’s hardly surprising that uninitiated observers haven’t noticed this transport ‘bracket creep'.