The councils, working under a Community Connecting South banner, are also calling for Armadale Road to be upgraded to a dual carriageway between Verde Drive in Jandakot and Anstey Road in Forrestdale.
The CCS partnership is chasing $160 million from the state and federal governments for the flyover bridge and freeway interchange, and a further $130 million commitment by 2018 for work on the 7km stretch of Armadale Road.
They say addressing infrastructure needs will unblock the "enterprise arc" in the south, boosting productivity and employment.
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READ NOWAnd they are willing to make it an election issue, preparing a four-week campaign in the lead-up to September's Canning by-election.
Cockburn Mayor Logan Howlett said traffic issues at Cockburn Central had spread beyond peak periods.
And it is little wonder when close to 20,000 people have moved to within 5km of the precinct in the past decade.
"The important issue is to have the Federal Government and Opposition recognise the need for this crucial infrastructure investment, hence the focus is on obtaining a promise of funding," Mr Howlett said.
"The construction program would take several years to complete as it is not on the current State Government capital works plan, which is why the two local governments are seeking to make it a key electoral issue."
Like Cockburn Central's quick growth, Piara Waters, Forrestdale and Harrisdale have added 16,000 residents over the past decade.
The Metropolitan Redevelopment Authority's Forrestdale Business Park is expected to house 700 businesses and 15,000 workers.
Armadale Mayor Henry Zelones said the upgrades would make Armadale Road a spine servicing growing residential and business communities.
"The speed of residential and industrial development along Armadale Road continues to outpace all expectations and has placed increased pressures on the Nicholson Road-Armadale Road and Wright Road-Armadale Road intersections," he said.
�These transport corridors are major contributors to the state's economy, (linking to) ports, industrial areas, and freight and logistics industries.
"Congestion erodes business competitiveness and impacts negatively on productivity, employment and business attraction and restricts job growth."