A truck carrying metal debris spilled its contents and scattered it along more than 20km of southbound lanes of the M1 Motorway north of Sydney around 5am on Friday.
The debris slashed hundreds of tyres, including multiple tyres on some cars, the NSW transport department said.
"We've had 145 vehicles damaged and marooned due to burst tyres, but there is metal everywhere," NSW Transport Management Centre coordinator Howard Collins told 2GB Radio.
A 25-km stretch of the major arterial connecting the Central Coast to Sydney was closed while traffic has backed up another five kilometres further north.
A clean-up operation comprised of emergency crews and sweepers is under way.
Dozens of tow trucks have been dispatched to around 200 drivers, NRMA spokesman Peter Khoury said.
The trucking company behind the metal spill apologised and pledged to foot the bill for impacted drivers
"We're very sorry for all the concern," Daniel Falconer of NJ Ashton Group told 2GB.
"Thank God that no one's had a major accident or anything."
Drivers of B-double trucks were advised to park up until the motorway reopens.
Other drivers are advised to use the old Pacific Highway instead.
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