Modifying trailers in NSW
The following guidelines are for owners wishing to modify their NSW registered low-ATM trailers (trailers with an ATM of 4500kg or less).
Modifications by the manufacturer
Trailers may be modified by the original trailer manufacturer, or in accordance with the trailer manufacturer's instructions.
Where a trailer is modified in a way that may affect the trailers compliance, the manufacturer may provide a letter of compliance for the trailer stating the ways in which the trailer has been modified and that it continues to comply with the applicable vehicle standards. Such a letter is to contain the manufacturers letterhead and be signed by the manufacturers chief engineer or manager of compliance.
Where these changes affect the vehicles registration details, an adjustment of records inspection is to be obtained from an appropriate inspection station. The examiner is to ensure that all changes have been made according to the manufacturers letter.
Some examples of such changes may be:
- GTM/ATM re-rating
- Replacement of braking systems with those of another type (for example, the replacement of an over-run braking system with an electric braking system)
If the trailers manufacturer cannot be determined, then this option to show compliance will not be applicable to your trailer.
Modifications outside of the manufacturer’s instructions
If a trailer is modified outside of instructions issued by a manufacturer, the trailer will require certification by a Vehicle Safety Compliance Certification Scheme (VSCCS) Licensed Certifier.
For a list of VSCCS Licensed Certifiers, please see VSCCS Bulletin 1.
For more information on modifying trailers, contact Technical Enquiries on 1300 137 302 or email technical.enquiries@transport.nsw.gov.au.
Trailer mass ratings
Modifications to trailer design and components can affect the trailers allowable GTM and ATM ratings and should be considered carefully and done in accordance with advice either from the trailers manufacturer or a VSCCS Licensed Certifier.
Gross Trailer Mass
A trailers GTM is the allowable mass that the trailer may impose onto the road when connected to a tow vehicle and does not include any weight imposed on the tow vehicle through the trailers coupling.
A trailers GTM is measured by placing a measuring device under all the trailer’s tyres when connected to a tow vehicle.
Aggregate Trailer Mass
A trailer’s ATM is the allowable total mass of the trailer including any mass imposed on the tow vehicle through the trailer coupling.
A trailer’s ATM is measured by placing a measuring device under all of the trailer’s tyres and the tow coupling or jockey wheel, when the trailer is not connected to a tow vehicle.
Trailer braking systems
Trailer braking system requirements are based on the Gross Trailer Mass (GTM) rating of a trailer and are given in the Australian Design Rules for trailer braking systems (ADR 38).
The table below gives a summary of the minimum braking system requirements for low-ATM trailers. Trailers may be fitted with a braking system that meets higher GTM requirements but must not be fitted with one that does not meet the minimum requirement shown.
| Trailer GTM | Minimum Brake System Requirements | Breakaway brake system required? |
|---|---|---|
| 0-750kg | Exempt from the requirement to fit brakes. | No |
| 751-2000kg |
| No |
| 2001kg GTM-4500kg ATM |
| Yes. Trailer brakes must apply and remain applied for 15 minutes in the event of a trailer becoming disconnected from the towing vehicle. |
For more information on the construction requirements of low-ATM trailers, go to Vehicle Standards Bulletin 1:
- Trailers manufactured after 30 June 2023 or complied under the Road Vehicle Standards Act 2018 see VSB 1 Revision 6.
- Trailers manufactured on or before 30 June 2023 or complied under the Motor Vehicle Standards Act 1989 see VSB 1 Revision 5.