This article is about road trains that carry freight. For trackless trains that carry passengers see trackless train, for other trains see train (disambiguation).

A road train is a truck design used in remote areas of Australia, United States and Western Canada to move bulky loads efficiently.

A road train consists of a relatively conventional truck chassis, cab, and engine unit, but instead of pulling a single trailer the road train pulls a succession of them, typically three but sometimes more, providing massive carrying capacity.

Road trains are unwieldy, and pulling and maneuvering them safely is only possible because of the lack of traffic on Australia's outback roads, and the terrain's flatness. The multiple trailers are detached and connected individually to multiple trucks when the road train gets close to populated areas.

Road trains are used for transporting all manner of materials, with livestock transport the most common. The cost-effective transport they have made possible has played a significant part in the economic development of these remote areas.

Overtaking a road train can be quite difficult (and on Australia's many dirt roads often impossible). Patience, assistance from the driver, and large amounts of clear road are required. Many road train drivers assist by blinking their right-hand turn indicators a couple of times to indicate that the road ahead is clear. It is common for passing motorists to flash both turn indicators to say "thanks" after a successful passing maneuver.

Road Train DSC03680.jpg|300px|thumb|left| A Road train being unloaded off itself at Timber Creek.]] When the Road Train trailers are empty it is common practice to stack the trailers. At various points along the Highways special loading ramps are provided for stacking and unstacking the trailers. This is commonly referred to as "dog-up" or "dogging-up". In the more remote or less travelled areas the loading ramps are often just dirt or gravel pushed up to form a ramp. Quite often diff locks are required when dogging-up because of wheel slip on the loose surfaces.

In the United States, trucks on public roads are limited to three trailers (in some states only two), and the term "road train" is not commonly used. 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 (such as ore or aggregate) hauling in the interior west.

In the far north of Canada, road trains are used to transport materials on winter roads.

World's longest road trains

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In 1999 the town of Merredin, Western Australia 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 603 metric tons and measuring 610 metres were pulled by a Kenworth truck for 8 km.

In 2003, the record was surpassed near Mungindi, New South Wales, by a road train consisting of 87 trailers and a single prime mover (measuring 1235 metres in length). ^*

The next record was 1,442 metres, set by a driver in Kalgoorlie, Western Australia in a Kenworth owned by Doug Gould. In 2006, a truck with 104 semi-trailers (at a length of 1,474.3 metres) claimed a new record at Clifton, Queensland. ^*

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