The Western Australian government has unveiled its preferred design and location for a new container terminal in Kwinana, just south of the port of Fremantle.

A new terminal has been planned for several years, with modelling said to consistently show that Fremantle Port and its surrounding roads will reach capacity within the next two decades.

Fremantle, south of the state capital, Perth, imports and exports around 800,000 teu annually, but this is expected to grow to more than 3m teu over the next 50 years.