Frequently Asked Questions

Frequently Asked Questions

In Australia, a heavy vehicle has a gross vehicle mass (GVM) or aggregate trailer mass (ATM) over 4.5 tonnes. Only changes that affect design, safety, or compliance need approval. Small additions like extra lights, aerials, or air-conditioning usually do not require it if the vehicle stays compliant. Major or safety-related changes such as suspension work, chassis modifications, or mass rating upgrades must be approved by an engineer under the Heavy Vehicle Modifications Code (VSB6).

A VASS (Vehicle Assessment Signatory Scheme) certificate is an engineer’s approval for a heavy vehicle modification. It confirms the work meets all required standards. Any heavy vehicle over 4.5 tonnes GVM modified under VSB6 rules needs a VASS certificate. This approval is accepted across Australia.

Any change to structure or systems that affects safety or compliance often needs certification. Examples include suspension upgrades, brake changes, chassis or wheelbase adjustments, custom body mounts, tow coupling or fifth wheel installation, and changes to mass ratings (GVM, ATM, GCM). Accessories like extra lights or radio aerials usually don’t require it.

Only a certified engineer, known as an Approved Vehicle Examiner (AVE) or VASS signatory can approve and certify heavy-vehicle modifications. They inspect the work and issue the compliance certificate required for the modification to be legally recognised.
Certification ensures the modification meets safety and legal standards. It keeps the vehicle roadworthy and compliant with national Heavy Vehicle Standards. Without it, a modified heavy vehicle may be unsafe, illegal to drive, or fail registration checks.
Timeframes vary with the engineer’s schedule and the complexity of the work. After passing inspection and providing all documents, most certificates are issued in a few days. Some engineers offer faster service for urgent cases.
FEA is a computer simulation used to predict how structural changes will perform in real use. Engineers use it to test the strength and durability of changes like chassis extensions or body mounts before approval.
Only a Chartered Engineer can legally certify heavy vehicle modifications. Their approval confirms the work meets all Australian Design Rules and safety requirements.
Yes. Certificates from approved engineers in other states are generally valid nationwide. You don’t need to recertify when moving or selling the vehicle across states.