Australia's most complex underground junction will come under scrutiny as MPs probe what went wrong with the billion-dollar Sydney interchange and how to fix the resulting gridlock.
Inner-city traffic has been thrown into chaos since the opening of the $3.9 billion Rozelle Interchange in late November, with a series of attempted fixes failing to alleviate widespread peak-hour jams.
A NSW parliamentary inquiry will investigate the design, traffic modelling and implementation behind the so-called "spaghetti junction", which includes 24km of tunnels and completes the $20 billion WestConnex motorway - the nation's largest road project.
It will also look into what led to asbestos contamination in garden mulch at the adjoining Rozelle Parklands, which was created as part of the motorway works in the city's inner west.
Premier Chris Minns pointed to minor changes made around the interchange - including to merging lanes and traffic-light sequences - when asked on Thursday about the government's solutions to fix the controversial project.
Roads Minister John Graham said it could take six months for traffic to "settle down" in the area.
But Greens MP and transport committee chair Cate Faehrmann earlier described the project as a "complete disaster" and said frustrated commuters deserved answers.
"Questions abound in relation to the traffic modelling that was undertaken," she said in backing the inquiry on Wednesday night.
"Who in their right mind would think that reducing 10 lanes of traffic down to four and funnelling them all into the CBD would magically work and be this fantastic transport solution?"
"This inquiry will examine the decisions that led to this debacle. Importantly, we'll look at solutions to this mess."
The project was meant to provide faster access to the city centre for millions of people from western and southwest Sydney.
Inner West Council mayor Darcy Byrne also backed the inquiry, calling the design an "infrastructure disaster".
"One week since the return of schools and peak traffic it's now clear the traffic chaos at the Rozelle Interchange is permanent and caused by a defective design," he said.
"This interchange is one of the most costly and disruptive mistakes in the history of Sydney's motorway network and those responsible must be held to account."
Mr Graham said the government welcomed the additional scrutiny and noted changes made to the original design in the days after its opening "seem to have improved things significantly".
"But there are clearly still issues," he said.
Shadow treasurer Damien Tudehope said the inquiry would be a "witch-hunt and blame game" over the project, which began under the former coalition government.
Mr Graham and motorway operator Transurban, as well as independent experts and residents, will report to the inquiry.
