The first major stage of WestConnex is now expected to be opened next month but motorists may not gain a toll-free period because of fears it will attract too many vehicles and cause major congestion to its tunnels in Sydney's inner west.

A month-long toll free ride was introduced when a widened section of the M4 motorway between Homebush and Parramatta was opened two years ago. Other motorways in Sydney such as the Cross City and Lane Cove tunnels have had toll-free holidays following their openings.

While a toll-free period for the M4 East has been under consideration, it is understood officials harbour concerns it will lead to a surge in traffic volumes, and severe congestion at on and off ramps from tunnels onto Wattle Street at Haberfield, and the connecting City West Link.

The entrance to the M4 East tunnels at Haberfield in Sydney's inner west. Credit:Steven Siewert

It underscores the challenges the operator will have managing public expectations of WestConnex. Proponents argue many of the benefits, such as a predicted reduction in traffic on Parramatta Road, will not be fully realised until the third stage – tunnels linking the M4 and M5 – is open by 2023.