Roads and Maritime Services (formerly Roads and Traffic Authority) is committed to safely monitoring and managing air quality within Sydney's tunnels, as well as within surrounding communities. Motorway tunnels take cars off local streets, improving surface air quality. Inside the tunnels, sophisticated measurement and ventilation systems ensure that air quality meets the strict regulations governing emissions levels.

How is air quality managed in the Sydney Harbour Tunnel?

Air quality in the tunnel is managed with a ventilation building located in the northern pylon of the Sydney Harbour Bridge. In addition to air being expelled via the ventilation building, air is expelled through the tunnel portals (tunnel entrances and exits). Air is circulated through the tunnel by a combination of vehicle movements and the use of jet fans. Fresh air is drawn into the tunnel by an intake located on the top or side of each tunnel.

Air quality monitoring

The Sydney Harbour Tunnel has a comprehensive air quality management system. The tunnel is fitted with 22 carbon monoxide monitors as well as air velocity and direction monitors. There are 14 supply and 16 reversible exhaust fans located throughout the tunnel, ensuring that air quality is maintained. The reversible fans also allow extraction of smoke in the event of a vehicle fire in the tunnel.