Quad Axle Group : A group of four axles in which the horizontal distance between the centrelines of the outermost axles is more than (3)2 m but not more than (4)9 m
Peter Milne and Kieran Sharp, ARRB Group, and Bob Ungers, consultant, Austroads Glossary of Terms (4th Ed.), Austroads Ltd., Sydney, NSW, Australia 2010. http://www.bicyclensw.org.au/files/u1/Austroads_Gl ossary_of_Terms_4th_edition.pdf (Road Trfc and Transp Sfty - Brit) {529}