WA govt defends $440 million Perth waterfront project

A report by transport consultants Veitch Lister says the controversial project - which aims to transform Perth's central riverfront into a smaller version of Sydney's Circular Quay - will slow CBD traffic to a crawl and add 10 minutes to peak-hour commutes.

WA Opposition Leader Mark McGowan on Wednesday said the rapidly growing city was already "massively congested", and that the plan to re-route busy Riverside Drive would make it worse.

"We've always been supportive of some sort of development down here, but now with this report it shows there will be significant traffic congestion, significant inconvenience," he said.

"Why didn't the government come up with a better option?"

McGowan, however, says there is very little he can do to scrap or redesign the project, even if he wins next year's election.

"The premier has already said all of the contracts will be signed," he said.

"(But) we would have a look at anything that can be done to try to make the situation better."

Transport Minister Troy Buswell said the project - recently christened Elizabeth Quay in honour of the Queen's jubilee - would cause minimal disruption.

"Traffic planning has always been part of this project," he said.

"The displacement effect from changes to Riverside Drive is minimal and will be catered for in the existing road network."

He admits Perth's traffic congestion will still need to be addressed, suggesting a tunnel may be built under the city.

"At some stage, we're going to have to consider alternate significant investments in road infrastructure - in particular around the CBD - to cater for growth.

"You don't transform cities without some changes to the way we use those cities."