New temperature projections support climate-responsive pavement design

Tuesday, 10 November 2026

New Austroads research provides 20-year pavement temperature projections across Australia and New Zealand to help road agencies account for changing climatic conditions when designing asphalt and foamed-bitumen pavements and selecting sprayed seal surfacings.

The research projects a general increase in Weighted Mean Annual Pavement Temperature (WMAPT) and Maximum Pavement Surface Temperature (Tmax), two critical parameters used in Austroads pavement design guidance. The largest increases are projected for parts of northern and western Australia, while changes are generally more moderate in New Zealand, with some southern locations showing decreases in WMAPT.

“Temperature is an important input into pavement design and material selection. By looking 20 years ahead, this research gives road agencies more locally relevant information to consider how changing temperatures may affect the pavements being designed today,” said Joanne Vanselow, Austroads’ Environment and Sustainability Program Manager.

The study used regionally downscaled climate projections from CSIRO for Australia and Earth Sciences New Zealand (formerly NIWA) for New Zealand. To manage uncertainty between individual climate models, researchers used an ensemble approach that averages outputs from multiple models under intermediate and high emissions scenarios (SSP2-4.5 and SSP5-8.5).

The projected changes could have practical implications for pavement design. Under the current Austroads mechanistic-empirical design methodology, higher WMAPT values generally reduce the design flexural modulus and fatigue life of asphalt, potentially resulting in thicker asphalt layers. Higher Tmax values can also influence the binder grade and sprayed seal treatment selected for hotter conditions.

The findings vary considerably by location. Northern and western Australia generally show the greatest increases, with locations including Camooweal, Tennant Creek and Kununurra among those showing the largest changes in WMAPT. Western Australia recorded some of the most notable projected changes in Tmax.

“The regional differences are important. Roads operate in very different climatic conditions across Australia and New Zealand, so understanding how pavement temperatures may change at a local level gives agencies a stronger basis for considering future design and material requirements.”

The research recommends further work to consider how the findings could inform future updates to the Austroads Guide to Pavement Technology Part 2: Pavement Structural Design and Austroads Guide to Pavement Technology Part 4K: Selection and Design of Sprayed Seals. It also identifies opportunities to validate projected temperatures against field measurements and assess the performance of asphalt, foamed bitumen and sprayed seals under changing temperature conditions.

Download Long Term Projections of Weighted Mean Annual Pavement Temperature and Maximum Pavement Surface Temperature.