Opposition transport spokesman Alistair Coe will make the party's latest infrastructure announcement on Monday, which he said would end bottlenecks between McCulloch Street in Curtin and the Tuggeranong Parkway.

The plan is the second major spending pledge from the opposition in four months, and comes a year before the election campaign begins. In June, the opposition committed to spending $146 million the duplication of Gundaroo Drive and a new flyover on the Barton Highway near Gungahlin.

Mr Coe said the price tag for the work had been developed using the government's own costings from a 2013 design study by engineering services firm SMEC Australia. It found the duplication project would cost $23.3 million. The opposition has added cost for inflation to 2015 dollars and additional 10 per cent contingency for overruns.

Associated work including tree removal and sound barriers is included in the proposal.

The government's costings were released to the opposition under freedom of information laws. Works approval for the project was granted by the National Capital Authority in May this year.

Last week Chief Minister Andrew Barr told the Legislative Assembly insufficient scrutiny had been given to opposition policy announcements to-date.

The June announcement, days before the government released its latest budget, included $51 million for the leasing and operation of 50 buses for ACTION, including pay for more drivers. Earlier this month Opposition Leader Jeremy Hanson said the party would introduce a four-year halt to lease variation charges for development activity in the city and town centres of Tuggeranong, Woden, Belconnen and Gungahlin.

The opposition is yet to announce a substantive public transport policy, expected to go up against the government's plans for a $783 million light rail line to Gungahlin. The Liberals are attempting to frame the election through sustained opposition to the tram line.

A Liberal government would prioritise the Cotter Road project.

"This is an obvious missing link in the Cotter Road duplication," Mr Coe said.

"The government has flagged that they believe it is a road that warrants duplication but they didn't fund it at the time of doing the first stage of the Cotter Road duplication. It is also going to become more important as more and more houses are developed in Molonglo."

"There's no doubt that there is considerable congestion, especially in the morning peak, going north-east bound, on the Cotter Road. It is getting worse as more cars enter the road from the Molonglo Valley. The Canberra Liberals believe it needs to be done as a priority."

The duplication would benefit travel into and out of the city, as well as suburbs in Canberra's south including Fyshwick and the parliamentary triangle.

"I think it is required for Canberra and people are looking for these sorts of core municipal services to be delivered. There is an expectation that a local government can and should be delivering road infrastructure for a growing part of the city and that is exactly what Weston Creek and the Molonglo Valley is," he said.

Mr Coe forecast more infrastructure and policy announcements from the opposition in 2015. He said growth areas and obvious missing links would receive priority.