Trailer brake requirements
Brake rules are based on GTM, the weight carried by the trailer's own wheels. ATM includes the towball download as well, so GTM is always a little lower.
| GTM | Brakes | Override brakes | Breakaway |
|---|---|---|---|
| Up to 750 kg | Not required | n/a | No |
| 751 to 2,000 kg | On at least one axle | Allowed | No |
| Over 2,000 kg | On every wheel, controlled from the vehicle | Not allowed | Yes, holds for 15 minutes or more |
Earlier versions of these rules allowed unbraked trailers only with a single axle. If your trailer has two axles and is close to 750 kg, check with your state transport authority.
Safety chain requirements
| ATM | Chains | Standard and rating |
|---|---|---|
| Up to 1,000 kg | 1 | AS 4177.4, 1,000 kg designation (6.3 mm link) |
| Up to 1,600 kg | 1 | AS 4177.4, 1,600 kg designation (8 mm link) |
| Up to 2,500 kg | 1 | AS 4177.4, 2,500 kg designation (10 mm link) |
| 2,501 to 3,500 kg | 2 | AS 4177.4, 3,500 kg designation (13 mm link) |
| 3,501 to 4,500 kg | 2 | Grade T steel, 800 MPa minimum, each with a breaking load above the ATM |
Link sizes are from the Western Australian and Tasmanian guidance on VSB 1. Chains should be as short as practical and, when there are two, crossed under the coupling. Shackles connecting chains to the towbar must be rated too: WA's guidance asks for a breaking load of at least 1.5 times the trailer's ATM.
Coupling requirements
- Up to 3,500 kg ATM: a quick-release coupling with positive locking and a second locking device you can see is engaged. 50 mm ball couplings must comply with AS 4177.3 and are rated 750, 2,000 or 3,500 kg.
- Over 3,500 kg ATM: a coupling that complies with ADR 62 (or UN R55), such as a pintle or a heavy-duty off-road coupling rated for the ATM.
The towbar, towball and coupling must each be rated for the trailer. The lowest rating is your limit.
Common questions
- At what weight does a trailer need brakes in Australia?
- Over 750 kg GTM. At or below 750 kg GTM brakes aren't required. VSB 1 and Transport for NSW both base the brake rules on GTM, the weight on the trailer's wheels.
- Can I use override (over-run) brakes on a caravan?
- Only up to 2,000 kg GTM. Over 2,000 kg GTM the brakes must act on every wheel and be controlled from the tow vehicle, which in practice means electric or electronic brakes with a brake controller.
- When do I need a breakaway system?
- Over 2,000 kg GTM. If the trailer separates from the vehicle, the breakaway system must apply the trailer brakes immediately and keep them on for at least 15 minutes.
- How many safety chains does my trailer need?
- One chain up to 2,500 kg ATM and two chains over 2,500 kg ATM. The chain rating depends on the ATM: 1,000, 1,600, 2,500 or 3,500 kg designations to AS 4177.4, and Grade T steel chain over 3,500 kg ATM.
- Is a 50 mm towball OK for a 3,500 kg trailer?
- A 50 mm ball coupling to AS 4177.3 can be rated up to 3,500 kg ATM, provided the coupling, towball and towbar are all rated for it. Over 3,500 kg ATM you need a coupling that complies with ADR 62.
Sources
- Vehicle Standards Bulletin 1 (Revision 6): trailers with an ATM of 4.5 tonnes or less (August 2026), Australian Government, Department of Infrastructure
- Towing a trailer or caravan, NSW Government (Transport for NSW)
- Safety chains and shackles for trailers under 4.5 tonnes ATM (CI-119C), Department of Transport, Western Australia
- Light trailer requirements: compliance with VSB1, Transport Tasmania
- A guide to trailer brakes, RACQ
Rules checked against these sources on 12 October 2026. See rules, sources and method.