Infrastructure Australia chief executive Romilly Madew said Australia's infrastructure needs were rapidly increasing, with the economy becoming more urbanised. "This infrastructure boom that we are in is the new normal," she said. "If we don't continue this investment, the costs of congestion will double." The biggest cost of the congestion is found on the major roads into Sydney and Melbourne, with travel times and delays expected to soar. Sydney

Loading The most congested road by 2031 in Sydney would be the four kilometre stretch between North Sydney and the city centre via the Harbour Tunnel. The agency estimated 84 per cent of the run effectively would be spent sitting still, with the delay put at 19 minutes. Other heavily congested roads would include the run between Mount Druitt and Westmead on the M4, the M5 between Liverpool and Sydney Airport and Ashfield into the CBD via the Anzac Bridge. The longest commute would be for motorists driving from Lucas Heights to Ryde West via the A6, with the delay 67 minutes on the morning commute and 63 minutes on the afternoon return. The cost of all this congestion was expected to double to $15.7 billion annually over the next 12 years. For those using public transport, the cost of crowding on trains and buses was expected to reach $223 million compared to $68 million today.

Melbourne By 2031, the most congested road in Melbourne would be the Hume Freeway between Donnybrook and the M80 Ring Road, with drivers facing a 39-minute delay on their daily morning run. It would be little better on the afternoon return, with the delay forecast to be 31 minutes. Other big delays could be expected between Gisborne South and the Tullamarine Freeway, from the airport into central Melbourne and from Epping into the CBD via High Street. The longest delay would be on the run from Geelong into the city on the Princes and West Gate freeways at 69 minutes in the morning. Over the length of a full day, a person driving between Pakenham and the Melbourne CBD would spend almost two hours extra in their vehicle because of congestion.

The cost of all the congestion across Melbourne would rise from $5.5 billion now to $10.4 billion annually by 2031. The cost facing public transport users in terms of crowding would rise to $352 million from $75 million. Infrastructure spending The congestion costs take into account the expected benefits to flow from $200 billion in major construction work already under way or planned in major cities, putting pressure on state and federal governments to ramp up activity. The Reserve Bank of Australia has urged all governments to lift their infrastructure spending to help support the economy while also helping to make cities more efficient for their residents.

Ms Madew said the Morrison government should re-examine 103 projects sitting on the regulator's priority list, describing them as "ready to go". "The infrastructure priority list is a pipeline," she said. "Funding could be used to drive what the RBA governor has been saying as part of an investment in infrastructure stimulus." Challenging times Outside of better private and public transport, Infrastructure Australia said there were a range of challenges facing much of the nation.

Technological change, such as self-drive semi-trailers, would help Australia deal with some of the problems but they in turn were creating new ones. The advent of online shopping meant there would be an increase in the number of small trucks delivering goods in residential streets that were not built to take such vehicles. Loading Replay Replay video Play video Play video Many state governments used demountable classrooms to deal with surging student populations but these were not adequate to meet with expected demand, nor conducive to good learning. "Without changes to the way demand is evaluated and new capacity provided, schools in fast-growing cities will be unable to meet growing demand, risking reduced quality of education outcomes," Infrastructure Australia found.