The WestConnex tunnels were designed for safe traffic flow at 90km/h.
The speed limit will be raised from the current 80km/h on April 20 following work to update and integrate digital motorway systems and subject to final testing and commissioning.
The change is underpinned by a comprehensive safety and systems review by Transport for NSW post the opening of Rozelle Interchange, the final piece of WestConnex.
The new speed limit will apply to the mainline tunnels between Homebush and Beverly Hills.
The change comes after a speed limit increase on the M5 South-West in October last year. The speed limit eastbound on the M5 South-West between Belmore Road at Riverwood and King Georges Road at Beverly Hills returned to 100km/h after being reduced to 80km/h prior to the opening of the M8 in 2020.
The WestConnex adjustment will be introduced on a weekend and inside NSW school holidays to give motorists a chance to transition to the new speed limit.
Minister for Roads John Graham said:
“This is unequivocally good news for Sydney motorists who use WestConnex, getting them home that little bit sooner to spend time with family or across the city to make an appointment.
“This 10km/h change is being implemented with safety as the sole focus. These modern motorway tunnels were designed specifically for traffic moving safely at 90km/h and now that WestConnex is complete we are adjusting the speed limit accordingly.
“This is a pragmatic approach. Where we can increase speed limits safely, getting people to work, home or study faster, we will do so. On the flipside to that, the NSW Government works with communities that have concerns about local safety to adjust speed limits lower.”