Lucy Turnbull says Sydney needs projects like WestConnex to ease congestion Photo: Jessica Hromas

The WestConnex motorway project is a "rational" response to the city's congested roads, says the chief of the Greater Sydney Commission, Lucy Hughes Turnbull.

"A lot of the WestConnex task is catching up with things that really should have happened 15 to 20 years earlier," Mrs Turnbull told The Australian Financial Review's National Infrastructure Summit, adding that Sydney did not have enough connections between the city and southern regions.

"It is a very rational response to a major congestion challenge that we face ... we need to move forward and do it."

Mrs Turnbull acknowledged planners needed to "get the balance" right between developing new infrastructure to meet the needs of a rapidly expanding city, and community engagement.

"Often when you clearly express the growth challenge that we face, and how little time in the time scale of own lives we have to deliver that, I think people begin to understand the challenges."

The WestConnex project has been controversial, with local communities opposing the disruption to neighbourhoods.

Better transport links throughout Sydney would help boost jobs in western Sydney, particularly Parramatta which is becoming a "major hub" for health, education, government and administrative services, said Mrs Turnbull, who was appointed chief commissioner in December.

"The whole footprint of Sydney is changing…the rate of transformation and change is unprecedented in my memory."

Badgerys Creek - the site of the new, planned airport 50 km west of the CBD - should be encouraged to become a major new economic zone, while strong local governments were needed to manage the challenges of growth, she said.

"Powering up local government is a very good and important objective for the future … I don't think there is a correlation between the size of local government and the quality of decision making."

The Greater Sydney Commission plans to provide annual infrastructure priority lists from next year.