B-double

So-called -"double" in Australia partly because of industry concerns about negative public attitudes to road trains.^[1] The "B" refers the load sharing axle group of the bridge "B" lead trailer with a 5th wheel coupling at the rear (between the trailers)- followed by a 5th wheel/turntable connected semitrailer as the second in the configuration.^[2] B-Doubles were initially developed in Canada, as B-Trains. The Australian freight road industry was able to persuade Governments to call them B-Doubles. This was to reduce potential confusion with road trains and also help overcome some public opposition that persisted, in some urban areas, to the mid-1990s. Note: the "A" in Road-Train nomenclature refers to the "A-Frame" drawbar inherent to many "dog-trailer"/dolly converter type of trailer (ie. when a semitrailer is converted into a Dog-trailer by the inclusion of a 2 or 3 axle "Dolly" Converter (containing a 5th wheel coupling), the assumption is that all trailer types are being hauled by a Semi-PrimeMover (Articulated Tractor unit) via a 5th wheel/turntable connection).

Calling the "Lead-trailer" the "A", or calling a regular semi trailer in the train a "B" trailer - or vice versa, confuses the reason why the A and B are used and overlooks that both the A-converter and B-Trailer, are in reality types of dolly (both are also registered as individual trailers) which convert a semitrailer into a self steering unit (dog trailer) - following the lead. A "B"-trailer (bridge) carries a load supported between the leading 5th wheel/turntable (mounted on either; another trailer, a dolly converter or the hauling tractor/PrimeMover) and its wheelset, while sharing its (rear) wheelset with the semi-trailer following on the turntable connector, while the "A" dolly-converter generally carries no load on the drawbar and places no (significant) load (or roll forces) in the leading trailer (or tractor) unit.

B-double (plural B-doubles)

1. (Australia) A truck and trailer combination consisting of a prime mover coupled to two trailers without the use of a dolly-converter with a drawbar (A-coupling).
   • 2001, Philip Laird, Mark Bachels, Back on Track: Rethinking Transport Policy in Australia and New Zealand, page 38:

     B-Doubles were initially developed in Canada, as B-Trains.

   • 2011, OECD, Moving Freight with Better Trucks: Improving Safety, Productivity and Sustainability‎^[2], page 248:

     Australian B-doubles generally have eight or nine axles, with increasing interest in Quad-axle B-doubles for some applications, including the carriage of two 40 foot containers through urban areas.

   • 2011, Sophia Rendell, Brisbane Valley Underbelly‎^[3], page 87:

     I mean there were the little things like the B-double that was allowed in the town and actually allowed to park in the street until it was ready to leave on its next trip. Not only is this illegal but a B-double is not allowed to leave the designated route at any time.

• road train