The new M4 tunnels, which are part of WestConnex, will bypass 22 sets of traffic lights from Homebush to Haberfield. It will also reduce up to 20 minutes off a trip from Parramatta to the Sydney CBD.
The 5.5-kilometre twin tunnels will be three lanes in each direction and extend the widened M4 from Homebush to Haberfield.
It is expected that the M4 tunnels will reduce the traffic volume on Parramatta Road by 53 per cent by 2021.
Minister for Roads Andrew Constance said within two years it is expected about 67,000 trips will be made through the new M4 tunnels each day.
"WestConnex will take up to 10,000 trucks a day off Parramatta Road, which is welcome news for anyone who sits in bumper to bumper traffic on that notoriously congested corridor," Mr Constance said.
"I would like to thank communities for their patience throughout construction over the past three years."
The WestConnex project also includes the new M5, the M4-M5 Link and the Rozelle Interchange.
