Melbourne freeway reopens after road repair fault causes major pile-up, commuter delays

All citybound lanes of Melbourne's Princes Freeway in Werribee have been reopened after "human error" during a road repair caused dozens of crashes and a truck rollover.

Motorists faced delays of up to four hours this morning after a broken expansion joint on inbound lanes of the freeway, between the Princes Highway and Duncans Road, caused a major pile-up.

It's understood contractors were in the process of replacing a broken expansion joint on the road when they placed a temporary metal plate over it about 3am.

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Believing the road surface was safe, crews left the scene, but within an hour a steel joint came loose and snagged the wheel of a truck, causing it to flip about 4.20am.

That crash then triggered a pile-up of up to 10 cars, closing multiple lanes of traffic for up to 10 hours.

No one was injured.

The pile-up triggered commuter chaos across the Werribee and Wyndham Vale areas, with traffic banking up on surrounding roads as well as the freeway.

The Department of Transport and Planning confirmed all lanes of the freeway reopened about 2.30pm, but minor delays may remain.

"A reduced speed limit of 60km/h is in place until crews return tonight to complete repairs to the road surface. Transport Victoria thanks the community for their patience," a department spokesperson said.

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Department of Transport and Planning executive director of maintenance Michael Bailey apologised "unreservedly" for the impact and potential vehicle damage caused.

"For each driver that was impacted we encourage them to call us on 13 11 70 or jump online at transport.vic.gov.au and complete the documents that they need to, to let us know that they have been impacted, who they are and what that impact was," he said.

Bailey said expansion joints are typically bolted in and filled with bitumen to keep them in place.

He said the department would investigate whether all steps were correctly completed by contractors.

"It is part of our standard routine maintenance program that we fix expansion joints on bridges.

"Typically, the steel plates are put down and we can reopen the roads.

"Overnight, one has come loose, we believe through human error and we believe that has caused the damage."

The same contractors will finish replacing the expansion joint tonight, Bailey said.

"They're in a bit of shock. When they left the site, they believed it was safe," he said.

"For at least 10 years we've been working with them, they've done hundreds of expansion joints for us and without any issue," he said.

"They're one of our preferred contractors and at this stage we'll continue to work with them."