A proposed light rail extension to the Defence precinct at Russell would replace a dedicated bus lane currently being added to Constitution Avenue as part of delayed upgrade works.
Private consortiums being considered for the $800 million light rail line linking the city and Gungahlin have been asked to including costings for tracks on either side of a central median strip which will feature newly planted pin oak trees.
Spruiked as "Canberra's Champs-Elysees", Constitution Avenue has been a construction site since March 2014 as part of works funded by the ACT government with a $42 million contribution from the Abbott government to mark Canberra's centenary in 2013.
ACTION bus commuters have seen months of detours as a result of the project.
Roadworks would return to the area between Vernon Circle and Anzac Parade if the government decides to go ahead with the 3.2-kilometre extension running from the proposed terminus on Northbourne Avenue at Alinga Street, around London Circuit and down Constitution Avenue.
The bus lanes would be removed to make way for the additional tram tracks, which would not be immediately side-by-side, as with the 12-kilometre line on Northbourne Avenue.
A government spokesman said the current upgrades had been planned to require the minimal amount of additional work to install light rail tracks but some changes would see the configuration altered to create one combined general traffic and bus lane in each direction.
With three passenger stops, the proposed extension to Russell could increase daily passenger trips by as much as 5600 or 30 per cent. The extension would increase the cost of the public private partnership project.
On Thursday, Planning Minister Mick Gentleman said the road's southern side would soon include a separated three-metre wide shared path with improved pedestrian and cycling crossing points at traffic lights.
When finished, the roadway will feature new street furniture made from hardwood jarrah, brass and powder coated steel; new lighting, tree surrounds and planter boxes, drinking fountains, bus shelters, bike racks and bin enclosures.
Mr Gentleman said the long term aim for Constitution Avenue was to create a strategic road corridor, that also featured an appealing urban space for travel, work and socialising.
"Constitution Avenue is a key element of the Walter Burley Griffin master plan and, as the third leg of the parliamentary triangle, the road is significant in the implementation of the Griffin legacy," he said.
About 300 English oak trees were in place before the road upgrades began. More than 120 trees, including some that were failing, were removed. The first stage of the replacement program will see 230 mature English and pin oaks planted, including some taller than 10 metres.
A row of crepe myrtles will be added to the southern verge. The species were chosen for their visual appearance and structural nature, suited to narrow alignments.
English oaks will also be used to fill gaps along the road, including in the large work site space on the corner of London Circuit.
Opposition transport spokesman Alistair Coe said most Canberrans would agree the roadworks were taking a long time to be completed.
"Hopefully the finished product is worth the wait and I think what the plans are, if they are lived up to in reality, will be an avenue which I think is befitting for the national capital," he said.
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