As part of Tuesday's territory budget, $24.6 million will be allocated for duplication of the road from Erindale Drive to Ellerston Avenue – a bigger price tag and smaller scope of works than promised by ACT Labor in the 2012 election campaign.

In September 2012, former chief minister Katy Gallagher promised a re-elected Labor government would spend $19.6 million to upgrade Ashley Drive between Erindale Drive and Johnson Drive.

Citing public safety and access for public buses, the work was due to be completed by the 2015-16 financial year.

However, a new announcement by Chief Minister Andrew Barr and Roads and Parking Minister Mick Gentleman on Wednesday has pushed completion out by three years.

Mr Gentlemen defended the spending and said it was good news for Tuggeranong, despite the delay, smaller size and increased cost.

He said the current single carriageway carried more than 20,000 vehicles each day.

"We need to make sure we deliver the best for the residents of Tuggeranong, so we're delivering the best in engineering standards for the duplication as well.

"Currently the road from Ellerston to Johnson Drive isn't up to capacity. No doubt there will be an invitation later on when that capacity does rise to extend that duplication ... we will work on that through budget deliberations as well."

Asked why the entire duplication project was not going ahead as part of the current plan, Mr Gentleman said the project needed to be well staged with traffic management planning.

He did not directly answer questions about how drivers would manage changing lane conditions in the area.

"Most of the traffic feeding into this area comes off suburbs that are to the northside of Ellerston Avenue so we will see that as the engineering answer to that question," Mr Gentleman said.

The planned upgrades are designed to improve the north and southbound on-road cycle lanes, see additional footpaths added to more effectively link with off-road walking paths.

Existing underpasses near Statton Street and Bugden Avenue will also be duplicated.

A six-week community consultation on the plans was held in late-2014 and received more than 150 submissions from the public. Mr Gentleman said themes raised included calls for a pedestrian bridge over Monks Creek to connect Monash with the facilities along Ashley Drive, as well as noise walls being extended to the eastern side of Ashley Drive near Gowrie.

ramp metering traffic signals; and new traffic signals to improve flow at the intersections of Ashley Drive and Bugden Avenue, and Statton Street and Clift Crescent.

Former ACT Labor senator Kate Lundy, now an NRMA director, and Tuggeranong Community Council member Wayne King joined the announcement.

Mr Barr has flagged a "suburban" focus for Tuesday's budget and said the duplication was part of a broader roads package for Canberra.

"Our focus and delivery of this budget has been to invest in suburbs and to invest in areas that will improve the efficiency of our city, make people's daily commute easier, get people to work on time and to assist in improving the day-to-day lives of Canberrans."

Mr Barr said the government would seek to leverage investment to stimulate jobs and economic activity.

Already the government has announced $11 million for a Tuggeranong campus for the Canberra Institute of Technology, with courses to begin in 2016.