Road train

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.
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 They displaced bullock teams for the carriage of minerals to port and were, in turn, superseded by railways.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 6 m (19 ft 8 in) Dyson four-axle self-tracking trailers. At 130 hp (97 kW), 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 1.5 m (4 ft 11 in) 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 200 mi (320 km) 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).
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 200 tonnes (197 long tons; 220 short tons).
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.
In South Australia, B-triples up to 35.0 metres (114 ft 10 in) and two-trailer road trains to 36.5 metres (119 ft 9 in) 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 7,200 kilometres (4,500 mi) of key routes permitted to operate vehicles over 30 m (98 ft 5 in) 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 1 km (0.62 mi) 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 53.5 metres (175 ft 6 in) long and 136 tonnes (134 long tons; 150 short tons). 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.
In the United States, trucks on public roads are limited to two trailers (two 28 ft or 8.5 m and a dolly to connect; the limit is 63 ft or 19 m end to end). Some states allow three 28 ft or 8.5 m 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 53 ft or 16 m trailer and an additional 28 ft or 8.5 m 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).
In Finland, Sweden, Germany, the Netherlands, Denmark, Belgium, and some roads in Norway, trucks with trailers are allowed to be 25.25 m (82.8 ft) long. In Finland, a length of 34.5 metres (113 ft) 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 18.75 m (61.5 ft) (Norway 19.5 m or 64 ft). The trucks are of a cab-over-engine design, with a flat front and a high floor, about 1.2 m (3.9 ft) 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, 34-metre (111.5 ft) long, 82-tonne (81-long-ton; 90-short-ton) 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 90 t (89 long tons; 99 short tons) and measuring 30 metres (98.4 ft) and haulers for two 40 ft containers, measuring 32 metres (105 ft) in total. In 2015, a pilot began in Finland to test a 104-tonne timber lorry which was 33 metres (108 ft) 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 25.25 metres (82.8 ft) 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 25.25 metres (82.8 ft) 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.
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;
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.
In Zimbabwe, they are only used in one highway, Ngezi – Makwiro road. They make use of 42 m long road trains pulling three trailers.
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 Sssociation of India (ARAI). Currently, road trains are only permitted to operate on Mumbai-Nagpur Expressway.
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 35.5 t (39.1 short tons) and is capable of carrying 50 t (55.1 short tons) 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.
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 27.5 m (90 ft 3 in) 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.
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 35.0 metres (114 ft 10 in) and two-trailer road trains to 36.5 metres (119 ft 9 in) are generally only permitted on specified routes, including access to industrial and export areas near Port Adelaide from the north.
In 2018, B quad was also allowed in states Victoria, New South Wales and Queensland, which enables more economical transport.
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.
In South Australia, larger road trains up to 53.5 metres (175 ft 6 in) (three full trailers) are only permitted on certain routes in the Far North.
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 consists of one standard trailer and B-triple units linked with a converter dolly.
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.
In some parts of Australia, 'super quad' road trains up to 60 metres (196 ft 10 in) are permitted, consisting of four standard trailers connected via three converter dollies.
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.
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.
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:
If a vehicle had an X as the second letter, its mass limits were in line with the western states mass limits, which were:
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.
Australian road trains have horizontal signs front and back with 180 mm (7.1 in) high black uppercase letters on a reflective yellow background reading "ROAD TRAIN". The sign(s) must have a black border and be at least 1.02 m (3.3 ft) long and 220 mm (8.7 in) high and be placed between 500 mm (19.7 in) and 1.8 m (5.9 ft) 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.
Operational weights are based on axle group masses, as follows:
Therefore,
The Australian national heavy vehicle speed limit is 100 km/h (62 mph), except New South Wales and Queensland where the speed limit for any road train is 90 km/h (56 mph). 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 80 to 100 km/h (50 to 62 mph) on two-lane roads and between 100 and 110 km/h (62 and 68 mph) on three-lane roads.
In Europe, the speed limit for heavy goods trucks is usually 80 km/h (50 mph). There is a law on having speed limiters which makes it impossible to drive heavy trucks faster than 90 km/h (56 mph). 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.
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.