ACT transport minister Meegan Fitzharris said the introduction of traffic lights to the roundabout took motorists some getting use to, but had improved safety.

"Between January and December 2017 a total of 47 accidents were reported at the intersection compared to an average of approximately 100 accidents per year from 2012-2015 prior to works starting," Ms Fitzharris said.

The government released data divided by financial year to make its case.

In the 2014-15 financial year, there were 112 crashes at the intersection, with 108, 82 and 110 crashes in each financial year before that respectively.

"Further analysis of the performance of the intersection will continue to be undertaken in 2018 including crash data and travel patterns," Ms Fitzharris said.

The upgrades were made to tackle congestion in Canberra's north, with Gungahlin being Australia's second-fastest growing region. Up to 46,000 vehicles travel through the intersection each day.

"[S]ince the traffic lights became operational in December 2016 there have been no [formal] complaints regarding delays or queuing at the intersection," Ms Fitzharris said.

"The range of roadworks across the Gungahlin district impact the travel patterns of drivers through the network, so full appreciation of the impact and effectiveness of the intersection improvements will not be clear until these works are completed."

The $10 million upgrade, funded by the federal government, was a then-election commitment for the ACT Labor government, with the ACT Liberals proposing a $35 million flyover as an alternative.

The NRMA backed the Liberal proposal as the "best outcome" but planning minister said the cost could cost about $50 million.

The Barton Highway intersection was Canberra's most dangerous intersection, recording the most crashes, 515, between 2010 to 2014.

It was followed by the Coranderrk Street/ Parkes Way intersection, with 427 crashes, and the Anzac Parade/ Parkes Way intersection, with 289 crashes, during the same period.