Editing Road train (section)

===B-double===
[[File:Lindsay Transport B-Double.jpg|thumb|500px|A B-double parked at a truck stop in [[New South Wales]], Australia]]
[[File:Truck Spotting on the A58 E312 Direction Kruiningen-Netherlands 17 04 2020. (49784067867).jpg|thumb|A 25.25 metre B-double consisting of two trailers with the same length in the [[Netherlands]]]]
A B-double consists of a prime mover towing a specialised lead trailer that has a [[fifth wheel coupling|fifth-wheel]] mounted on the rear towing another semi-trailer, resulting in two [[articulated vehicle|articulation points]]. It may also be known as a '''B-train''', interlink in South Africa, B-double in Australia, tandem tractor-trailer, tandem rig or double in North America. They may typically be up to {{cvt|27.5|m|ftin}} long. The [[fifth wheel coupling]] is located at the rear of the lead (first) trailer and is mounted on a "tail" section commonly located immediately above the lead trailer axles.<ref name="code">{{cite web |url=https://www.nhvr.gov.au/files/t115-sa-code-of-practice-b-doubles.pdf |title=Code of Practice for B-Doubles |id=MR 414 06/11 |publisher=Government of South Australia, Department for Transport, Energy and Infrastructure |date=June 2011 |access-date=8 February 2016 |page=3 |archive-url=https://web.archive.org/web/20161021064819/https://www.nhvr.gov.au/files/t115-sa-code-of-practice-b-doubles.pdf |archive-date=21 October 2016 }}</ref> In North America this area of the lead trailer is often referred to as the "bridge". The twin-trailer assembly is hooked up to a tractor unit via the tractor unit's fifth wheel in the customary manner.

An advantage of the B-train configuration is its inherent stability when compared to most other twin trailer combinations, the turntable mounted on the forward trailer results in the B-train not requiring a converter dolly as with all other road train configurations.<ref>{{cite web |url=https://equipmenthunt.com.au/news/into-the-details-all-about-road-trains/ |title=Into the Details: All About Road Trains |publisher=Equipment Hunt Group Pty Ltd |date=April 2019 |access-date=9 April 2019 }}</ref> It is this feature above all else that has ensured its continued development and global acceptance.<ref>{{cite journal |doi=10.1080/03081068908717423 |title=Dynamic stability of B-doubles |last1=Sweatman |first1=P. |last2=Tso |first2=Y. |date=29 July 1988 |journal=Transportation Planning and Technology |volume=14 |issue=2 |pages=159–169 }}</ref> Reversing is simpler as all articulation points are on fifth wheel couplings.

B-train trailers are used to transport many types of load and examples include tanks for liquid and dry-bulk, flat-beds and curtain-siders for deck-loads, bulkers for aggregates and wood residuals, refrigerated trailers for chilled and frozen goods, vans for dry goods, logging trailers for forestry work and cattle liners for livestock.

In Australia, standard semi-trailers are permitted on almost any road. B-doubles are more heavily regulated, but routes are made available by state governments for almost anywhere that significant road freight movement is required.<ref name="RAVNet SA"/>

Around container ports in Australia exists what is known as a super B-double; a B-double with an extra axle (total of 4) on the lead trailer and either three or four axle set on the rear trailer. This allows the super B-Double to carry combinations of two 40 foot containers, four 20 foot containers, or a combination of one 40 foot container and two twenty foot containers. However, because of their length and low accessibility into narrow streets, these vehicles are restricted in where they can go and are generally used for terminal-to-terminal work, i.e. wharf to container holding park or wharf-to-wharf. The rear axle on each trailer can also pivot slightly while turning to prevent scrubbing out the edges of the tyres due to the heavy loads placed on them.