The independent body, which provides advice to the federal government, on Tuesday released the 2019 Australian infrastructure audit and a supplementary report looking congestion on urban transport.

That supplementary report paints a concerning picture for the Illawarra.

The report predicts several key roads will hit peak-hour capacity by 2031.

"Key access routes into Wollongong from inner northern suburbs such as Fairy Meadow and Corrimal, as well as southern areas like Dapto and Albion Park, will be affected by congestion," the report stated.

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Windang Road, the motorway and part of the Princes Highway between Unanderra and Dapto are also predicted to reach capacity in the morning peak, as is Bulli Pass.

The road links between the Illawarra and Sydney are expected to get worse by 2031; in terms of "total delay hours" the corridor will be the third-worst Sydney road for congestion in the AM peak and the second-worst for the run home.

While population growth in Wollongong is only expected to increase by around 8 per cent by 2031, the Dapto-Port Kembla population will climb by 19 per cent and Kiama-Shellharbour by 21 per cent.

Similarly, the pressures on transport in the region will also jump over the next decade.

"Car trips are forecast to increase by 19 per cent, and public transport by 30 per cent," the congestion report stated.

"Between 2016 and 2031 the average weekday cost to the Illawarra region of road congestion is forecast to grow from $500,000 to $1.1 million."

The growth in the Macarthur area will also put strains on Appin and Picton roads, leading to longer travel times for Illawarra residents.

"The Illawarra region would therefore find itself relatively isolated from the benefits of business investment and employment growth around Sydney's second airport," it found.

The trains between Wollongong and Sydney are predicted to become even more of a crush from Bulli north.