Wednesday, 17 June 2026
Austroads has updated its Guide to Pavement Technology Part 4K: Selection and Design of Sprayed Seals, with Edition 1.4 introducing targeted improvements to support more reliable, cost-effective road sealing across Australia and New Zealand.
Sprayed seals are widely used across the region, and the Austroads design method underpins how road agencies calculate binder application and aggregate spread rates. Ongoing changes in traffic loads, pavement structures and materials have driven the need for timely updates to ensure the Guide remains fit for purpose.
Earlier this year, Austroads published AP‑T384‑26: Technical Basis for the Update of the AGPT, which identified priority areas to refine sprayed seal design methods and provided the technical foundation for this update.
Edition 1.4 incorporates findings from that technical report, along with insights from workshops held across Australia and New Zealand and a targeted literature review involving industry practitioners.
The update introduces practical improvements that can be implemented immediately, alongside areas identified for further research. Key changes include:
- corrected ‘seal’ definitions and updated technical figures
- removal and standardisation of certain treatment types and binder classifications
- expanded guidance on binder selection, including new advice for S9R/S9RF binders
- improved guidance for geotextile reinforced seals, including binder retention considerations
- simplification of design methods through the removal of the Average Least Dimension (ALD) nomograph option
These updates ensure the design method remains aligned with current practices, materials and operating environments across both countries.
“The goal is to align the Guide with modern practices, the current operating environment, and evolving selection criteria, and to develop strategies that would allow the Australian and New Zealand design methods to be integrated,” said Austroads Transport Infrastructure Program Manager Ross Guppy.
“This research draws together contributions from practitioners across Australia and New Zealand, supporting the development of design methods that are tailored to local environments, optimising performance and cost-effectiveness.”
The updated Guide supports road agencies, designers and contractors to deliver more consistent and reliable sprayed seals, particularly under increasing traffic volumes and changing material conditions.
By incorporating industry input and the latest research, the update helps improve decision-making, optimise performance and ensure cost-effective outcomes across diverse road networks.
Download
AP‑T384‑26: Technical Basis for the Update of the AGPT
Guide to Pavement Technology Part 4K, Edition 1.4 (February 2026)
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17 June 2026 at 1:00 pm AEST | Presented by Steve Patrick and Chris Skantzos.
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