From 5 September 2025, a new 46-metre vehicle underpass has opened beneath Mount Street at North Sydney, providing a dedicated southbound route for up to 10,000 motorists daily. This underpass connects drivers from the Warringah Freeway to the Cahill Expressway, offering access to the City East, Airport, and Eastern Suburbs.
Dylan Anderson
Benefits for Motorists and Bus Users
The new underpass is designed to ease congestion and improve journey reliability for motorists. Once the dedicated southbound bus lane opens next year, it will also streamline travel for thousands of buses, removing the need for merging and weaving, and providing uninterrupted access into the city.
How to Access the New Route
Motorists should remain left on the Warringah Freeway and use the newly opened section of the Kirribilli exit (Alfred Street North) to enter the Mount Street underpass. Signage has been installed to assist drivers. Those who miss the turn will need to detour via the Sydney Harbour Bridge and CBD before reconnecting with the Eastern Distributor.
Construction Methods
The underpass was constructed using advanced excavation technology, including a remote-controlled continuous miner that removed over 3,000 cubic metres of sandstone and rock. This technique reduced noise and disruption compared with traditional rock hammering. An ‘upside down’ construction method was used, with the roof built first to allow pedestrians to continue using Mount Street during excavation.
Dylan Anderson
Broader Project Context
The Warringah Freeway Upgrade is a key enabling project for the Western Harbour Tunnel, Sydney’s first new harbour crossing in 30 years. Together, these projects will improve connectivity between Sydney’s north, west, and airport precincts.
Daily Traffic Volumes
The Warringah Freeway is one of Australia’s busiest roads, with approximately 250,000 vehicles and 150,000 bus passengers using the corridor each day.
Dylan Anderson
Dylan Anderson
