www.nhvr.gov.au/safety-accreditation-compliance/chain-of-responsibility/regulatory-advice/managing-the-risk-of-a-light-or-empty-lead-trailer-in-a-laden-b-double
B-double with a significant load imbalance between the axle mass on the lead trailer and the axle mass on the rear trailer, the vehicle ride quality is is supported by desktop modelling, is to ensure that the mass on the drive axle group is at least 20% of the total