Roads ACT director Tony Gill said the new section of road was opened on Thursday afternoon and would improve travel times and safety.

"This follows the opening of the northbound section of road last week which allowed traffic to access the parkway from Fairbairn Avenue," he said.

"Southbound traffic has been able to use the Majura Parkway north of Tambreet Street since earlier this year but will now enjoy the benefits of a direct road between Canberra's north and city area."

Mr Gill said traffic management arrangements would remain in place at the Fairbairn Avenue interchange while the Molonglo River bridge and southbound exit were completed.

"Work to construct the Molonglo River bridge and Fairbairn Avenue bridge continues and once finished they will connect the Majura Parkway to the Monaro Highway," he said.

The $288 million Majura Parkway is Canberra's biggest construction project and was designed to provide a long-term solution for north-south through traffic.

The first sections of the dual carriageway were opened early this year on the northern end of the project.

Despite problems with contractors last year, the road was scheduled to open to traffic in mid-2016.