The plan could cost the NSW government more than $100 million a year, but the decision would not affect the funding of future road projects, the premier told reporters in Sydney on Monday.
"We've done our sums and each road project stands on its merit in terms of how we finance those road projects. We've ensured we have the capacity to continue to build into the future," Ms Berejiklian said.
Up to tens of thousands of drivers could save around $360 a year on their registration, she said, with the rebate backdated to July.
Ms Berejiklian said the rego rebate would not be an incentive for people who use public transport to instead hop in their cars.
"I want to make sure that people have every opportunity to use public transport, that's my preferred way of getting around, but obviously we also know that people also need to use toll roads," she said.
Drivers have avoided the M4 since a toll was imposed in August, but WestConnex Minister Stuart Ayres said the drop was in line with government forecasts.
"That's expected, that's what we said would happen, the traffic movements are playing out pretty much exactly how we forecast they would," Mr Ayres told reporters.
But social media users didn’t seem too pleased.
