One of Perth's most congested intersections will be overhauled as part of the McGowan Government's alternative to the scrapped Perth Freight Link project.

The Government has released details of the $118 million "congestion-busting" plan to upgrade High Street in Fremantle by 2020.

A roundabout will replace the existing traffic lights at the intersection of High Street and Stirling Highway — a frequently backlogged junction which slows heavy-haulage traffic heading to and from Fremantle Port.

A wide median strip will be built on High Street, with several houses which had previously been purchased by the Government to be demolished to accommodate this.

A new service road will be added for residents north of High Street.

A roundabout will replace the existing traffic lights at the intersection. ( ABC News: Jacob Kagi )

Premier Mark McGowan said the project was a smart alternative to the now-abandoned freight link, reducing congestion and improving safety along the heavy-haulage route at a fraction of the cost.

"What we are doing here is making it far, far easier for truck drivers to negotiate this corner and avoid the stop-start along High Street," Mr McGowan said.

Transport Minister Rita Saffioti said the safety and freight efficiency benefits would be significant.

"It is another project that is about improving congestion and increasing jobs," Ms Saffioti said.

Construction is set to commence next year and take about 18 months.

The project is due for completion by 2020. ( Supplied: WA Government )

The Government is yet to reach agreement with the operators of the Fremantle Golf Course, which will lose some land as a result of the road redesign, but Ms Saffioti said she was hopeful that would be concluded soon.

She said changes to the design of the High Street upgrade would reduce the impact on the golf course.

Liberals holding on to Perth Freight Link

But the State Opposition dismissed the project as "tinkering around the edges", saying it would only increase freight bottleneck issues.

Deputy Liberal leader Liza Harvey said the former government's Freight Link project would have provided a proper solution.

"This is one of those interim solutions that is not going to solve the problem," she said.

"That problem gets solved by Roe 8 and Roe 9."

Mrs Harvey maintained the Liberals would stick with the Freight Link as policy for the 2021 election, saying the project would go ahead if the party was returned to power in three years.