WestConnex is part of an integrated transport solution to address the needs of a growing city

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FAQs See all

Transferring vehicles from surface roads into free-flowing underground motorway tunnels will improve the air quality along existing surface roads where traffic is reduced.

For example, an independent air quality assessment detailed in the M4 East EIS found air quality will generally improve along the Parramatta Road corridor because of traffic shifting to WestConnex.

Motorists will have a smooth motorway to travel on, rather than being stuck in congested, stop-start traffic with traffic lights, and this will reduce emissions.

Our tunnels are also designed to reduce emissions, as they are generally flatter and less steep at the entries and exits.

Traffic modelling tells us the expected demand for WestConnex and the number of traffic lanes needed. The motorway has been designed to meet traffic demand now and in the future.

The number of lanes varies across the project: 

  • M4: the M4 Motorway has been widenedfrom three lanes in each direction to four lanes in each direction between Parramatta and Homebush. The new M4 East tunnels between Homebush and Haberfield will be three lanes in each direction.
  • New M5: when the tunnels open, there will generally be two lanes in each direction between Kingsgrove and St Peters. The tunnels can accommodate three lanes in each direction in future, with additional approvals needed for this change.
  • M4–M5 Link: The M4-M5 Link will provide twin underground tunnels with four lanes in each direction between Haberfield and St Peters.

For surface road sections of the motorway, including the widened M4, the speed limit will generally be 90km/h. In tunnels, the speed limit will be 80km/h, the same as for other tunnels in Sydney. A small section connecting to Sydney Airport may have a lower speed limit.