Definition of "road train"

Road trains are big rigs made of tractors that pull more than one trailer. […] They are driven in remote areas of Canada, the United States, and Australia. Australia is home to the largest road trains in the world. […] It is common for Australian road trains to have up to six trailers attached to a single tractor, with each trailer holding up to 140 tons (127 tonnes) of freight.

2007, Adrianna Morganelli, Trucks: Pickups to Big Rigs, page 17

Livestock road trains tend to travel in convoys and its[sic] best to pull over for a rest and watch them pass.

2007, Dick Eussen, Australia′s Savannah Way: Cairns to Broome, page 13

Where there are two semi-trailers and one motive unit this is called a double bottomed articulated vehicle or road train. Especially in Australia, road trains may consist of more than two trailers. In the UK, serious consideration is being given to their use on motorways.

2010, Alan Rushton, Phil Croucher, Peter Baker, The Handbook of Logistics & Distribution Management, page 398