Forty-five trees are earmarked for removal from the two London Circuit car parks being remodelled to make room for a tram construction compound in the Magistrates Court car park.
The government also plans to extend the Canberra Theatre car park on to the grassed hill behind, next to Vernon Circle. With access via ramps, the new area would fit 21 cars.
The government has applied to the National Capital Authority for approval for the work, with the authority now considering its response.
Overall, there will be 93 extra parks on the eastern side next to the Canberra Theatre complex (opposite the Sydney Building), for a total of 298.
On the western side, outside the Magistrates Court, the number of parks will drop by 68, to 203 in total.
The government's application to the authority said a number of the trees must go because they were in conflict with the car-park layout and some would be affected by the removal of kerbs and raised planters, exposing and damaging roots.
In the new car parks, 33 trees would be removed, and 74 would remain. Another 12 would be removed in the section of the Magistrates Court car park being turned into a construction compound.
The trees to be removed (in red) in the Magistrates Court car park. The trees in green remain.
Most of the trees are English elms or London planes. None of the trees were rare or endangered, the application said. Most were growing in adverse conditions, with the elms heavily pruned and many approaching over-maturity.
The boundary trees on London Circuit would be retained "where practical".
The stone wall at the back of the theatre car park would be affected for two ramps to be built to access the grassed areas behind.
The trees to be removed (in red) in the Canberra Theatre car park. The trees in green remain. Part of the new section of parks on the Vernon Circle grassed area is shown at the bottom of the image.
The ACT government concedes the new parking layouts don't meet its own code for new car parks, but says they don't need to because it's not a new car park and the current car parks don't meet the code in any case. Both would meet national standards and would retain the same number of disabled and motorbike parks, it says.
The remodelling is temporary and each car park has a "10-year design life", both earmarked for future development, it said.
The ACT code specifies at least three disabled spots for every 100 car parks, and at least three motorbike parks for every 100 car parks. The two car parks will have a total of 15 disabled and 35 motorbike parks.
The government's parking code says car parks should be as small as possible, about 75 parks or less, or at least separated into segments of about 75, with separate exits. Car parks should be "attractive, pleasant spaces in their own right", according to the code. "Large, unbroken expanses of paving are aesthetically unacceptable. Maximum use should be made of vegetation within the car park areas to soften the visual impact."
The code says about 15 per cent of surface car-park sites should be permanently landscaped with shade trees, shrubs and ground covers, with particular focus on shade trees.