B-double

A road train, also known as a land train or long combination vehicle (LCV) is a semi-trailer used to move road freight more efficiently than single-trailer semi-trailers. It consists of one semi-trailer or more connected together with or without a prime-mover. It typically has to be at least three trailers and one prime-mover. Road trains are often used in areas where other forms of heavy transport (freight train, cargo aircraft, container ship) are not feasible or practical.

History

Early road trains consisted of traction engines pulling multiple wagons. The first identified road trains operated into South Australia's Flinders Ranges from the Port Augusta area in the mid-19th century. They displaced bullock teams for the carriage of minerals to port and were, in turn, superseded by railways.

During the Crimean War, a traction engine was used to pull multiple open trucks. By 1898 steam traction engine trains with up to four wagons were employed in military manoeuvres in England.

In 1900, John Fowler & Co. provided armoured road trains for use by the British Armed Forces in the Second Boer War. Lord Kitchener stated that he had around 45 steam road trains at his disposal.

A road train devised by Captain Charles Renard of the French Engineering Corps was displayed at the 1903 Paris Salon. After his death, Daimler, which had acquired the rights, attempted to market it in the United Kingdom. Four of these vehicles were successfully delivered to Queensland, Australia, before the company ceased production upon the start of World War I.

In the 1930s/40s, the government of Australia operated an AEC Roadtrain to transport freight and supplies into the Northern Territory, replacing the Afghan camel trains that had been trekking through the deserts since the late 19th century. This truck pulled two or three Dyson four-axle self-tracking trailers. At , the AEC was grossly underpowered by today's standards, and drivers and offsiders (a partner or assistant) routinely froze in winter and sweltered in summer due to the truck's open cab design and the position of the engine radiator, with its cooling fan, behind the seats.

Australian Kurt Johannsen, a bush mechanic, is recognised as the inventor of the modern road train. After transporting stud bulls to an outback property, Johannsen was challenged to build a truck to carry 100 head of cattle instead of the original load of 20. Provided with financing of about 2000 pounds and inspired by the tracking abilities of the Government roadtrain, Johannsen began construction. Two years later his first road train was running.

Johannsen's first road train consisted of a United States Army World War II surplus Diamond-T tank carrier, nicknamed "Bertha", and two home-built self-tracking trailers. Both wheel sets on each trailer could steer, and therefore could negotiate the tight and narrow tracks and creek crossings that existed throughout Central Australia in the earlier part of the 20th century. Freighter Trailers in Australia viewed this improved invention and went on to build self-tracking trailers for Kurt and other customers, and went on to become innovators in transport machinery for Australia.

This first example of the modern road train, along with the AEC Government Roadtrain, forms part of the huge collection at the National Road Transport Hall of Fame in Alice Springs, Northern Territory.

In 2023, Janus launched the first BEV triple road train with 620 kWh battery, also the world's heaviest street-legal BEV truck at 170 tonnes (gross weight).

Usage

Australia

The term ''road train'' is used in Australia and typically means a prime mover hauling two or more trailers, other than a B-double. In contrast with a more common semi-trailer towing one trailer or semi-trailer, the diesel prime mover of a road train hauls two or more trailers or semi-trailers. Australia has the longest and heaviest road-legal road trains in the world, weighing up to .

Double (two-trailer) road train combinations are allowed on some roads in most states of Australia, including specified approaches to the ports and industrial areas of Adelaide, South Australia and Perth, Western Australia. An A-double road train should not be confused with a B-double, which is allowed access to most of the country and in all major cities.Hema Maps (Firm) & Martin, Ray. & Martin, Will. (2007), Australia truckies atlas artographic material: the complete atlas for the professional driver / Hema Maps; artography, Ray Martin and Will Martin– – has state by state routes and route restrictions I

In South Australia, B-triples up to and two-trailer road trains to were only permitted to travel on a small number of approved routes in the north and west of the state, including access to Adelaide's north-western suburban industrial and export areas such as Port Adelaide, Gillman and Outer Harbour via Salisbury Highway, Port Wakefield Road and Augusta Highway before 2017. A project named ''Improving Road Transport for the Agriculture Industry'' added of key routes permitted to operate vehicles over in 2015–2018.

Triple (three-trailer) road trains operate in western New South Wales, western Queensland, South Australia, Western Australia and the Northern Territory, with the last three states also allowing AB-quads (B double with two additional trailers coupled behind). Darwin is the only capital city in the world where triples and quads are allowed to within of the central business district (CBD).

Strict regulations regarding licensing, registration, weights, and experience apply to all operators of road trains throughout Australia.

Road trains are used for transporting all manner of materials: common examples are livestock, fuel, mineral ores, and general freight. Their cost-effective transport has played a significant part in the economic development of remote areas; some communities are totally reliant on regular service.

When road trains get close to populated areas, the multiple dog-trailers are unhooked, the dollies removed and then connected individually to multiple trucks at "assembly" yards.

When the flat-top trailers of a road train need to be transported empty, it is common practice to stack them. This is commonly referred to as "doubled-up" or "doubling-up". Sometimes, if many trailers are required to be moved at one time, they will be triple-stacked, or "tripled-up".

Higher Mass Limits (HML) Schemes are now in all jurisdictions in Australia, allowing trucks to carry additional weight beyond general mass limits. Some roads in some states regularly allowing up to 4 trailers at long and . On private property like mines, highway restrictions on trailer length, weight and count may not apply. Some of the heaviest road trains carrying ore are multiple unit with a diesel engine in each trailer, controlled by the tractor.

Diesel sales in Australia (per year) are around 32 billion litres, of which some is used by road trains. In order to reduce emissions and running cost, trials are made with road trains powered by batteries.

United States

In the United States, trucks on public roads are limited to two trailers (two and a dolly to connect; the limit is end to end). Some states allow three trailers, although triples are usually restricted to less populous states such as Idaho, Oregon, and Montana, plus the Ohio Turnpike and Indiana East–West Toll Road. Triples are used for long-distance less-than-truckload freight hauling (in which case the trailers are shorter than a typical single-unit trailer) or resource hauling in the interior west (such as ore or aggregate). Triples are sometimes marked with "LONG LOAD" banners both front and rear. "Turnpike doubles"—tractors towing two full-length trailers—are allowed on the New York Thruway and Massachusetts Turnpike (Interstate 90), Florida's Turnpike, Kansas Turnpike (Kansas City – Wichita route) as well as the Ohio and Indiana toll roads. Colorado allows what are known as "Rocky Mountain Doubles" which is one full length trailer and an additional trailer. The term "road train" is not commonly used in the United States; "turnpike train" has been used, generally in a pejorative sense.

In the western United States LCVs are allowed on many Interstate highways. The only LCVs allowed nationwide are STAA doubles.

On private property like farms, highway restrictions on trailer length and count do not apply. Bales of straw, for example, are sometimes moved in wagon trains of up to 20 trailers an eighth of a mile long (carrying a total of 3,600 bales).

Europe

In Finland, Sweden, Germany, the Netherlands, Denmark, Belgium, and some roads in Norway, trucks with trailers are allowed to be long. In Finland, a length of has been allowed since January 2019. In Sweden, this length has been allowed on several major roads, including all of E4, since August 2023. 34.5 meters allows two 40 foot containers.

Elsewhere in the European Union, the limit is (Norway ). The trucks are of a cab-over-engine design, with a flat front and a high floor, about above ground. The Scandinavian countries are less densely populated than the other EU countries, and distances, especially in Finland and Sweden, are long. Until the late 1960s, vehicle length was unlimited, giving rise to long vehicles to cost effectively handle goods. As traffic increased, truck lengths became more of a concern and they were limited, albeit at a more generous level than in the rest of Europe.

In the United Kingdom in 2009, a two-year desk study of Longer Heavier Vehicles (LHVs), including up to 11-axle, long, combinations, ruled out all road-train-type vehicles for the foreseeable future.

In 2010, Sweden was performing tests on log-hauling trucks, weighing up to and measuring and haulers for two 40 ft containers, measuring in total. In 2015, a pilot began in Finland to test a 104-tonne timber lorry which was and had 13 axles. Testing of the special lorry was limited to a predefined route in northern Finland

Since 2015, Spain has permitted B-doubles with a length of up to and weighing up to 60 tonnes to travel on certain routes. In July 2024, after 5 years of testing, HCTs have been permitted on Spanish territory, with lengths of up to 32 meters (105 ft) and 70 gross tonnes.

Since 2016, Eoin Gavin Transport, Shannon and Dennison Trailers, Kildare have been trialling B-doubles on the Irish motorways. In Feb 2024, The Pallet Network announced four B-doubles to operate between Dublin, Cork and Galway.

In 2020, a small number of road trains were operating between Belgium and the Netherlands.

Mexico

In Mexico road trains exist in a limited capacity due to the sizes of roads in its larger cities, and they are only allowed to pull 2 trailers joined with a pup or dolly created for this purpose. Recently the regulations tend to be more severe and strict to avoid overloading and accidents, to adhere to the federal rules of transportation. Truck drivers must obtain a certificate to certify that the driver is capable to manipulate and drive that type of vehicle.

All the tractor vehicles that make road train type transport in the country (along with the normal security requirements) need to have visual warnings like;

* "Warning Double Semi-Trailer" () alert located in the frontal fenders of the tractor and in the rear part of each trailer,
* yellow turn and warning lights to be more visible to other drivers,
* a seal for the entire vehicle approving the use as double semi trailer,
* federal license plates in every trailer, dolly, and tractor unit.

Some major cargo enterprises in the country use this form to cut costs of carrying all type of goods in some regions where other forms of transportation are too expensive compared to it due to the difficult geography of the country.

The Mexican road train equivalent form in Australian Standard is the A-Double form, the difference is that the Mexican road trains can be hauled with a long distance tractor truck.

Zimbabwe

In Zimbabwe, they are only used in one highway, Ngezi – Makwiro road. They make use of 42 m long road trains pulling three trailers.

India

On 15th February 2025 Volvo Trucks India and Delhivery a Gurgaon based logistics company unveiled India's first road train consisting of a Volvo FM 420 4x2 tractor and a B-Double combination of 24 ft lead trailer and 44 ft semi-trailer coupled via fifth wheel making total length of vehicle close to 80 ft. With approvals from Ministry of Road Transport and Highways (MORTH) and Automotive Research Association of India (ARAI). Currently, road trains are only permitted to operate on Mumbai-Nagpur Expressway.

Trailer arrangements

A-double

An A-double consists of a prime mover towing a normal lead trailer with a towing hitch such as a Ringfeder coupling affixed to it at the rear. A fifth wheel dolly is then affixed to the hitch allowing another standard trailer to be attached. Eleven-axle coal tipping sets carrying to Port Kembla, Australia are described as A-doubles. The set depicted has a tare weight of and is capable of carrying of coal. Note the shield at the front of the second trailer to direct tipped coal from the first trailer downwards.

Pros include the ability to use standard semi-trailers and the potential for very large loads. Cons mainly include very tricky reversing due to the multiple articulation points across two different types of coupling.

B-double

A B-double consists of a prime mover towing a specialised lead trailer that has a fifth-wheel mounted on the rear towing another semi-trailer, resulting in two 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 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. 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. It is this feature above all else that has ensured its continued development and global acceptance. 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.

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.

B-triple

B-triple
Same as B-double, but with an additional lead trailer behind the prime mover. The B-train principle has been exploited in Australia, where configurations such as B triples, double-B doubles and 2AB quads are permitted on some routes. These are run in most states of Australia where double road trains are allowed. Australia's National Transport Commission proposed a national framework for B-triple operations that includes basic vehicle specifications and operating conditions that the commission anticipates will replace the current state-by-state approach, which largely discourages the use of B-triples for interstate operation. In South Australia, B-triples up to and two-trailer road trains to are generally only permitted on specified routes, including access to industrial and export areas near Port Adelaide from the north.

B quad

In 2018, B quad was also allowed in states Victoria, New South Wales and Queensland, which enables more economical transport.

AB triple

An AB triple consists of a standard trailer with a B-Double behind it using a converter dolly, with a trailer order of Standard, Dolly, B-Train, Standard. The final trailer may be either a B-Train with no trailer attached to it or a standard trailer. Alternatively, a BA triple sees this configuration reversed, consisting of a B-double with a converter dolly and standard trailer behind it.

A-triple

In South Australia, larger road trains up to (three full trailers) are only permitted on certain routes in the Far North.

BAB quad

A BAB quad consists of two B-double units linked with a converter dolly, with trailer order of Prime Mover, B-Train, Dolly, B-Train.

ABB quad

ABB quad consists of one standard trailer and B-triple units linked with a converter dolly.

AAB quad

AAB quad consists of A-double and B-double units linked with a converter dolly. Alternatively, a BAA quad sees this configuration reversed, first the B-double, then the A-double.

A quad

In some parts of Australia, 'super quad' road trains up to are permitted, consisting of four standard trailers connected via three converter dollies.

C-train

A C-train is a semi-trailer attached to a turn table on a C-dolly. Unlike in an A-Train, the C-dolly is connected to the tractor or another trailer in front of it with two drawbars, thus eliminating the drawbar connection as an articulation point. One of the axles on a C-dolly is self-steerable to prevent tire scrubbing. C-dollies are not permitted in Australia, due to the lack of articulation.

Dog-trailer (dog trailer)

A dog-trailer (also called a pup) is a short trailer with a permanent dolly, with a single A-frame drawbar that fits into the Ringfeder or pintle hook on the rear of the truck or trailer in front, giving the whole unit two or more articulation points and very little roll stiffness. These are commonly used in Australia, particularly for end tipper applications like shown above. They are normally limited to a single dog trailer behind a short bodied (independently load carrying) truck with a standard length limit of 19 metres (20 under design permits). A quad dog trailer in combination with a bodied truck is able to carry more weight than a truck and single semi-trailer of the same length limit and access restrictions, as well as carrying two different materials as separate loads, such as with tipper bodies and fluid tankers.

Interstate road transport registration in Australia

In 1991, at a special Premiers' Conference, Australian heads of government signed an inter-governmental agreement to establish a national heavy vehicle registration, regulation and charging scheme: the Federal Interstate Registration Scheme (FIRS). Its requirements are as follows:

Due to the "eastern" and "western" mass limits in Australia, two different categories of registration were enacted. The second digit of the registration plate showed what mass limit was allowed for that vehicle. If a vehicle had a 'V' as the second letter, its mass limits were in line with the eastern states mass limits, which were:

* Steer axle, 1 axle, 2 tyres:
* Steer axle, 2 axles, 2 tyres per axle: Non load sharing suspension
** Load sharing suspension
* Single axle, dual tyres:
* Tandem axle, dual tyres:
* Tri-axle, dual tyres or 'super single' tyres:
* Gross combination mass on a 6-axle vehicle not to exceed

If a vehicle had an ''X'' as the second letter, its mass limits were in line with the western states mass limits, which were:
* Steer axle, 1 axle, 2 tyres:
* Steer axle, 2 axles, 2 tyres per axle
** Non load sharing suspension : Load sharing suspension
* Single axle, dual tyres:
* Tandem axle, dual tyres:
* Tri-axle, dual tyres or "super single" tyres:
* Gross combination mass on a 6-axle vehicle not to exceed

The second digit of the registration being a ''T'' designates a trailer.

One of the main criteria of the registration is that intrastate operation is not permitted. The load has to come from one state or territory and be delivered to another. Many grain carriers were reported and prosecuted for cartage from the paddock to the silos. However, if the load went to a port silo, they were given the benefit of the doubt, as that grain was more than likely to be going overseas.

Signage

Australian road trains have horizontal signs front and back with high black uppercase letters on a reflective yellow background reading "ROAD TRAIN". The sign(s) must have a black border and be at least long and high and be placed between and above the ground on the fore or rearmost surface of the unit.

In the case of B-triples in Western Australia, they are signed front and rear with "ROAD TRAIN" until they cross the WA/SA border where they are then signed with "LONG VEHICLE" in the front and rear.

Converter dollies must have a sign affixed horizontally to the rearmost point, complying to the same conditions, reading "LONG VEHICLE". This is required for when a dolly is towed behind a trailer.

Combination lengths

;B-double: max. Western Australia, max.
;B-triple: up to max.
;NTC modular B-triple: max. (uses 2× conventional B-double lead trailers)
;Pocket road train: max. (Western Australia only) This configuration is classed as a "Long Vehicle".
;Double road train or AB road train: max.
;Triple and ABB or BAB-quad road trains: max.

Operating weights

Operational weights are based on axle group masses, as follows:
;Single axle (steer tyre):
;Single axle (steer axle with 'super single' tyres):
;Single axle (dual tyres):
;Tandem axle grouping:
;Tri-axle grouping:

Therefore,
*A B-double (single axle steering, tandem drive, and two tri-axle groups) would have an operational weight of .
*A double road train (single axle steering, tandem drive, tri-axle, tandem, tri-axle) would have an operational weight of .
*A triple is .
*Quads weigh in at .
*Concessional weight limits, which increase allowable weight to accredited operators can see (for example) a quad weighing up to .

*If a tri-drive prime mover is utilised, along with tri-axle dollies, weights can reach nearly .

Speed limits

The Australian national heavy vehicle speed limit is , except New South Wales and Queensland where the speed limit for any road train is . B triple road trains have a speed limit of 100 km/h (62 mph) in Queensland.

In Canada, there has been no difference between the speed limits between cars and road trains, which range from on two-lane roads and between on three-lane roads.

In Europe, the speed limit for heavy goods trucks is usually . There is a law on having speed limiters which makes it impossible to drive heavy trucks faster than . These limits are normally the same for road trains. There is not a wish to encourage trucks to overtake slightly slower trucks on motorways because it obstacles the left lane, although common anyway e.g. when heavy road trains lose speed uphill.

World's longest road trains

Below is a list of longest road trains driven in the world. Most of these had no practical use, as they were put together and driven across relatively short distances for the express purpose of record-breaking.

*In 1989, a trucker named "Buddo" tugged 12 trailers down the main street of Winton.Doug's Tug
, the pick & shovel (13), December 2000.
*In 1993, "Plugger" Bowden took the record with a Mack CLR pulling 16 trailers.
*A few months later this effort was surpassed by Darwin driver Malcolm Chisholm with a , 21-trailer rig extending .
*In April 1994 Bob Hayward and Andrew Aichison organised another attempt using a 1988 Mack Super-Liner 500 hp V8 belonging to Plugger Bowden who drove 29 stock trailers measuring 439.169 metres a distance of 4.5 km into Bourke. The record was published in the next ''Guinness Book of Records''.
*Then the record went back to Winton with 34 trailers.
*On 3 April 1999, the town of Merredin, officially made it into the ''Guinness Book of Records'', when Marleys Transport made a successful attempt on the record for the world's longest road train. The record was created when 45 trailers, driven by Greg Marley, weighing and measuring were pulled by a Kenworth 10×6 K100G for .
*On 19 October 2000, Doug Gould set the first of his records in Kalgoorlie, when a roadtrain made up of 79 trailers, measuring and weighing , was pulled by a Kenworth C501T driven by Steven Matthews a distance of .
*On 29 March 2003, the record was surpassed near Mungindi, by a road train consisting of 87 trailers and a single prime mover (measuring in length).
*The record returned to Kalgoorlie, on 17 October 2004, when Doug Gould assembled 117 trailers for a total length of . The attempt nearly failed, as the first prime mover's main driveshaft broke when taking off. A second truck was quickly made available, and pulled the train a distance of .
*In 2004, the record was again broken by a group from Clifton, Queensland which used a standard Mack truck to pull 120 trailers a distance of about .
*On 18 February 2006, an Australian built Mack truck with 113 semi-trailers, and long, pulled the load to recapture the record for the longest road train (multiple loaded trailers) ever pulled with a single prime mover. It was on the main road of Clifton, Queensland, that 70-year-old John Atkinson claimed a new record, pulled by a tri-drive Mack Titan.

Outside Australia

*On 12 April 2016 in Gothenburg, Sweden, a Volvo FH16 750 pulled 20 trailers with double-stacked containers with a total length of 300 meters (984 ft) and with a total weight of 750 tonnes.

Gallery

File:Diamond T 980, National Road Transport Hall of Fame, 2015 (02).JPG, Kurt Johannsen's "Bertha" Diamond T 980
File:Sherwin-Williams Paints truck on US 95 (1).jpg, Sherwin-Williams Paints truck on US 95 Nevada
File:Side Dump Industries train set.jpg, Tipper A-double in USA
File:Road train (27).jpg, 53 foot container turnpike double in Canada
File:UPS Truck in Beatty Nevada (1).jpg, Triple trailer three 28.5-foot pups
File:Truck Spotting on the A16 Direction Zwijndrecht 19 04 2019.... Not the Best spot with the Barrier , But better than Nowt . (46728401165).jpg, A B-double with containers in the Netherlands
File:Terblanche Volvo FMX (18235690085).jpg, A-double in Africa
File:Road train at Zimbabwe border.jpg, B-doubles in Africa
File:Posto Shell Rei da Estrada.jpg, A-double in Brazil
File:Roe Hwy 140723 gn-02.jpg, Tri-axle prime mover with quad-axle trailers and tri-axle dolly in Australia
File:Greenmount 140723 gn-162.jpg, Two steer axled prime mover
File:B-Double road trains on Newell Highway or Jerilderie Street in Jerilderie, 2023.jpg, A B-double on Newell Highway
File:Road train (31).jpg, A-double
File:B-Triple road trains in Queensland, Australia, 2024, 02.jpg, A-triple
File:Kenworth K200, Border Village, 2017 (02).jpg, B-triple
File:B-Triple road train in Bourke, New South Wales, 2021.jpg, AB-triple
File:Road train (7).jpg, AAB quad
File:Road train in Mount Isa, Queensland, 2023.jpg, BAB quad

See also

* Air brake (road vehicle)
* Articulated bus
* Brake
* Containerization
* Container on barge
* Container ship
* Dolly (trailer)
* Federal Bridge Weight Formula
* Fifth wheel coupling
* Gladhand connector
* Intermodal freight transport
* Jackknifing
* Longer Heavier Vehicle
* National Network – highway and interstate system
* Overland train
* Ringfeder coupling devices
* Road transport in Australia
* Rolling highway – freight trucks by rail
* Semi-trailer truck – large trucks such as road trains and articulated lorries
* Shipping container
* Top intermodal container companies list
* Trackless train
* Transport

References

External links

Australian Road Train Association

Australian National Heavy Vehicles Accreditation Scheme.




South Australian Roads road train gazette

NSW Roads and Traffic Authority road train operators gazette

NSW Roads and Traffic Authority Restricted Access Vehicles route map index

NSW Roads and Traffic Authority Reflective sign standards


* ttps://web.archive.org/web/20060928154413/http://www.fhwa.dot.gov/policy/otps/truck/wusr/wusrindex.htm The U.S. Department of Transportation's Western Uniformity Scenario Analysis.
British Columbia Government Licensing Bulletin 6

British Columbia Government Licensing Bulletin 41

Roadmap of technologies able to halve energy use per passenger mile includes the dynamically coupled, heterogeneous type of roadtrain

Road trains and electrification of transportCombination Vehicles for Commercial Drivers License

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