The state and federal governments face their first test of their capacity to raise private funding to support the WestConnex motorway, opening talks with bankers and investors in the next couple of weeks.

The first stages of the motorway - a widened M4 and M4 East tunnels from Concord to Haberfield - are largely being paid for by taxpayers.

Chief executive of the Sydney Motorway Corporation, Dennis Cliche. Credit:Dominic Lorrimer

But the government hopes to raise about $1.5 billion off private investors to help fund the second stage of the motorway - new M5 East tunnels from Beverly Hills to St Peters.

To attract these investors, the government will sell the right to charge tolls on existing M5 East motorway tunnels, which opened without a toll in 2011, as well as the new M5 East tunnels to run along the same corridor.