Both parties are now promising to duplicate the major Gungahlin access road from the Federal Highway where it meets the new Majura Parkway all the way to Mulligans Flat, a stretch of about 6km, costing $57 million.

The Liberals are also promising a design study on a further extension which would duplicate the road all the way to Mirrabei Drive.

Liberal transport spokesman Alistair Coe said the work would alleviate a serious bottleneck where the new Majura Parkway feeds into Horse Park Drive.

"Nobody in Gungahlin would deny that this is absolutely essential," Mr Coe said. "Our commitment ... recognises the huge growth with the development of new suburbs like Bonner and Forde, as well as future development in places like Throsby, Moncrieff, Jacka and Taylor."

As the Liberals were preparing their announcement on Sunday, a video appeared on the My Gungahlin website on Sunday in which Transport Minister Meegan Fitzharris said the government was funding the $57 million duplication in the June budget.

The video is recorded during very windy conditions beside the road and is difficult to hear, but she later confirmed the announcement.

"I was pleased to confirm on Sunday that we will be upgrading all of Horse Park Drive from the Federal Highway to Mulligans Flat Road, and this work will be funded in this year's ACT budget," she said.

After seeing Ms Fitzharris announcement, the Liberals' extended their promised duplication, which was to have been from the Federal Highway to Gundaroo Drive, but now matches Labor's, with an extra 1.5km to Mulligans Flat Road and also matches Labor's $57 million of funding.

The tit-for-tat announcements are indicators that Labor and Liberal will compete to match promises for Gungahlin voters this year. The third seat in Gungahlin is attracting attention as the one that will decide the election, with whichever party takes the majority of seats there likely to form government.

The Liberals have already promised to duplicate Gundaroo Drive, at about $60 million, and build a flyover for the Barton Highway at Gungahlin, about $35 million. They have also committed to $4 million of work on Ashley Drive in Tuggeranong, where Labor also has work under way, and $25 million on duplication of the Cotter Road.

They have announced $51 million for 50 new buses, and set out a major reorganisation of the city's bus network, introducing six new direct rapid services along major routes, on top of the current two rapids.

They are yet to make announcements about changes to the Northbourne Avenue corridor, which might include a dedicated bus lane.

A discussion paper published by the party in December included a plan to build a 3.25-metre-wide one-way bus lane down the middle of the Northbourne median strip, with bike lanes alongside. Another option was a bus priority lane on the left-hand side of traffic, with a new median cycle path.

Labor's big-ticket transport item is the tram, with major work on the $700 million project set to begin at election time.