A major new toll road intended to ease traffic in Melbourne has finally opened, a decade after the project was first announced.

Victoria’s West Gate Tunnel, an alternative route to Melbourne’s west, opened to the public on Sunday morning with the long-awaited toll road heralded to be a “game-changer” for commuters.

The first trucks and cars passed through the 6.8-kilometre stretch just after midnight, drawing the $10.2 billion project to a close.

Victorian Premier Jacinta Allan described the roadway – which has three lanes in each direction – as a “massive game-changer for the way people travel around this great city and state”.

“It means families can get home sooner, congestion will be reduced, and most importantly, for residents here in the western suburbs, it will get trucks off local roads,” she said at the site.

Allan defended the Labor-backed project, despite a decade of turbulent planning, a doubling of its cost, and years of delays.

“This was a really complex project, and it did face some challenges on its journey,” she said.

“It’ll be also worth it in the decades ahead because as our city and state grows, this is exactly the sort of infrastructure we need to invest in today to support that growth into the future.”

The tunnel’s opening came two weeks after the opening of the Metro Tunnel rail project, the biggest upgrade to Melbourne’s rail system since the City Loop opened four decades ago.

It is expected to remove about 9000 trucks from local streets each day and slash commute times by up to 20 minutes.

The proposal was announced in 2014 with a price tag of $5.5 billion and a completion date of 2022.

The project has been the subject of controversy since then-Labor opposition’s Daniel Andrews campaigned to build the road in the lead up to the 2014 election and vowed to scrap a contract for the East West Link signed by the previous Liberal Napthine government if it was elected.

But cost blowouts and the discovery of toxic soil pushed the total bill for taxpayers to $10.2 billion and moved back its opening to late 2025.

The four-kilometre road links the West Gate Freeway at Yarraville, in Melbourne’s inner-west, with the Port of Melbourne and CityLink at Docklands.

A trip will set motorists back $4.09 for a car and $6.54 for a ute or van, and more than double that if they exit into the CBD’s west during morning peak hour.

Transurban is paying for $6.1 billion of the construction costs in exchange for operating tolls and a 10-year extension to its CityLink contract.

-AAP