The Liberals will announce their Northbourne plans on Wednesday. Deputy leader and transport spokesman Alistair Coe said the Northbourne work would cost up to $58 million with a generous contingency.

He said about 2.5 metres would be taken from each side of the centre strip on the main gateway road. That would reduce the width of the Northbourne median from about 27 metres to about 22 metres.

The extra road space would create enough room, when combined with the current kerbside bike lane, for four southbound and four northbound lanes of traffic on Northbourne Avenue from Barry Drive to Antill Street. One lane in each direction, adjacent to the kerb, would be a dedicated bus lane, with bus bays where possible.

Mr Coe said the bus lane was expected to bring travel times for a non-stop bus from the Gungahlin centre to the city at peak hour down to 18 minutes, and 30 minutes from any suburb of Gungahlin.

The central bike path would be three metres wide, and run all the way from the Gungahlin town centre to the city through the middle of the median. The bike lane would have its own lights, which would be phased with the traffic lights, allowing bikes to cross major intersections with the flow of traffic.

Work would begin early if the Liberals were elected to government, and Mr Coe believed he could re-purpose the light rail consortium to do the Northbourne construction work.

The announcement is the Liberals' answer to Labor's plans – already in early construction – for a 12-kilometres tram line from Gungahlin to the city down the middle of the Northbourne median strip.

Trams are to be given priority along the corridor, and traffic lights programmed to detect the approach of a tram and change to allow it through. Trams will run every six minutes during the morning and afternoon peaks, and the full journey will take 25 minutes, the same at peak and off-peak times.

The government's analysis in 2015 said, at the moment, buses travel every three minutes at peak times, taking 28 minutes in the morning and 26 minutes in the afternoon.

Mr Coe said he caught the bus from Gungahlin where he lives to the city at the peak morning time on Tuesday. It was not a non-stop service and was scheduled to take 28 minutes from the town centre. It took 31 minutes. Mr Coe believes his bus lane can knock as many as 10 minutes from the scheduled travel time.

He also believes he can carve as many as 2.5 metres from each side of the median strip without affecting many of the Northbourne Avenue trees. He says there is space in the middle for the bike lane without having to cut down trees.

Labor's light rail means the removal of all of the Northbourne Avenue trees – about 700 in all – and their replacement with new trees.

Labor's tram line has also been tied closely to the transformation of the Northbourne corridor. Buildings and land are being sold either side of the road for development and the government is embarking on the wholesale removal of public housing tenants from flats either side of the road so the sites can be sold and redeveloped.

The move has sparked Canberra's biggest rebuild of public housing. There are close to 400 public housing units in the precinct and, when combined with the sale of old public housing elsewhere in Canberra's inner north and inner south, the government is building or buying about 1300 new units.

Mr Coe said the Liberals would also redevelop the corridor, including the public housing, but not at the rate nor with the urgency of Labor. With no demand for large numbers of new apartments at the moment, the Liberals would be "far more strategic" about the corridor development, he said.

North of Antill Street and into Gungahlin, the Liberals would have just one south-bound bus lane. They would also build an extra traffic lane on each side of Flemington Rd and include lights to give buses priority at intersections.