PBS Split Axle Semi-Trailers: Increase Payload Without Increasing Tare
In the heavy transport industry, optimising payload without compromising tare weight is crucial. PBS split axle semi-trailers provide a cost-effective solution by increasing mass capacity through intelligent axle spacing—without the additional cost and weight of a quad axle configuration.
At Midlands trailers, we specialise in engineering design for high-performance semi-trailers designed for Australian conditions. Our expertise in vehicle trailer designs, approved under the Performance-Based Standards (PBS) scheme, ensures you move more—safely, efficiently, and with confidence. How Does Axle Spacing Increase Mass Capacity?
Under the General Mass Limits (GML), axle group load limits are capped to prevent excessive road wear. However, the sum of individual axle capacities in a group often exceeds the allowable group total. For example:
A single axle can legally carry 9 tonnes.
A tandem group is limited to 16.5 tonnes (8.25t per axle).
A tri-axle group is capped at 20 tonnes (6.66t per axle).
By splitting one or more axles from the group (with at least 2.5m spacing), each axle can carry closer to its full individual rating. A split tri-axle configuration, for instance, can carry 25.5 tonnes at GML, compared to just 20 tonnes with a closed tri-axle setup.
This strategy provides greater payload efficiency without increasing trailer tare or cost—an ideal option for operators looking to maximise return on every trip, with the management of tare trailer weight vitally ensuring optimal weight distribution.
Where Can PBS Split Axle Semi-Trailers Be Used?
PBS split axle semi-trailers must operate under the Performance-Based Standards (PBS) scheme.
Tier 1 Network Access is possible in some jurisdictions if the trailer is designed to full Tier 1 mass specifications.
Tier 3 PBS networks do not currently support split axle semis. Instead, operators must apply for point-to-point permits.
Western Australia (WA) and the Northern Territory (NT) currently do not permit split axle semi-trailers on their road networks.
At Midland, we ensure your trailer is a PBS-approved vehicle. We can help you navigate these requirements and design a compliant, high-performance PBS trailer tailored to your needs. Explore our PBS Trailers
Engineering Considerations for Split Axle Designs
To gain full PBS mass benefits, specific design and certification elements are required:
Steerable axle must be fitted to the split axle position for improved manoeuvrability.
Chassis reinforcement is essential to handle the additional stress at the axle interface.
Axle spacing must comply with the bridge formula to qualify for Tier 1 mass.
PBS assessments and certification are more involved than standard trailers, leading to higher upfront engineering costs.
At Midland, all trailers are engineered, sandblasted, and powder coated in Australia, ensuring maximum durability and long-term cost savings. Learn more about our manufacturing process
Alternatives to Split Axle Semi-Trailers
If PBS split axle trailers aren’t suitable for your network or operations, consider these high-mass alternatives:
Tri-Axle Semi-Trailers at HML (Higher Mass Limits)
Load capacity: 22.5 tonnes
Requires HML compliance and network access
Broader accessibility than split axle semis
Learn more about HML from NHVR
PBS Quad Axle Semi-Trailers at QML3
Load capacity: 27 tonnes
Approx. 1 tonne increase in tare
Available network access via PBS
PBS Quad-Axle Mass Limits – NHVR Info Sheet
Midland manufactures both options, with trailers designed to maximise payload and reliability. See our full trailer range
References
Maximise Payload with Precision-Engineered PBS Solutions
PBS split axle semi-trailers are a niche solution that, when used strategically for point-to-point hauls, offer superior payload capacity without additional tare weight and tare trailer mass. Midland provides full support from design through PBS approval, ensuring you're road-ready and fully compliant.
