The National Capital Authority has unveiled plans to dismantle on and off ramps on Kings and Commonwealth avenues, reduce speed limits and reconfigure the roads as grand boulevards for easy cycling and walking.
The speed limit would be cut to 60km/h on both roads under the proposals released by the authority on Monday for public consultation.
The plan would dismantle the clover leaf ramps that lead on and off Commonwealth Avenue on either side of Lake Burley Griffin, instead building conventional intersections, slowing traffic and opening up land either side of the avenue for development. Slip lanes would be eliminated, slowing traffic and giving more of the space to pedestrians and cyclists.
The light rail line would run not in the median strip, but on the roadway alongside it on Commonwealth Avenue (or Kings Avenue if it is re-routed there).
The National Capital Authority said the current state of the roads did not reflect their crucial ceremonial and symbolic roles. The landscape was fragmented, and the character of the streets had been eroded by the dominance of cars.
"The avenues are lacklustre and run down in appearance, and provide little support either for the buildings fronting them or for the uses to which these spaces are put. They act as a barrier rather than as a connector between the national triangle and its surrounding uses," the report said.
Large sections were missing from tree plantings and the avenues were difficult to cross and not pedestrian or cyclist friendly. They would remain important traffic routes, but would give priority to pedestrians and cyclists.
The English and Chinese elms, planted in the 1960s, lacked "the expected grandeur, spatial structure and character" and would be replaced by oaks in stages.
The verges on either side would have a paved wide outer path on the road verge, then a central zone with plantings, and an inner path.
The roads would be reconfigured to include a dedicated wide cycle lane both directions. The light rail line would run alng the lane adjacent to the median. On Commonwealth Avenue, a new route would be built for pedestrians and cyclists to get to Capital Hill and Parliament House.
The median strips would remain at 12 metres, with the extra space for bike paths and the light rail carved out of the existing roadway. The central and median lanes would be made narrower, dedicated right-turn lanes and left-turn slip lanes would be removed, intersections would be signalised and on and off ramps would be replaced with "more conventional urban intersections that reduce approach and departure speeds".
Land would be opened up for new buildings on both avenues "increasing the density of buildings and activity within the Parliamentary Zone", including future office blocks. Space is set aside for the National Gallery to expand towards Kings Avenue.
Two sites off Bowen Drive on the Kingston side of Kings Avenue are identified for future development. A number of development sites are earmarked off Kings Avenue at Russell, where Blamey Square would be rebuilt to become "one of the national capital's important symbolic and ceremonial spaces", with the carpark removed.
The West Basin development and sites near a raised London Circuit are set aside for development, in line with the ACT government's plans for apartments and commercial development in the area.
National Capital Authority chief executive Malcolm Snow said the proposals were a "high-level design", with detailed work to follow later in the year, followed by a business case to the commonwealth for funding probably in the 2018-19 financial year.