Roads and Maritime Services have conceded they did not anticipate the huge increase of westbound traffic after the eastbound overpass opened near Maitland Train Station, according to government documents.
The RMS documents obtained through Freedom of Information state that westbound queues had tripled from 200-300 metres before the overpass opened to 900 metres by July 2018, which was "inconsistent with the original modelling for the project".
The documents were sourced by Maitland MP Jenny Aitchison, who spoke about the traffic snarl in her first speech in the new NSW Parliament last week. She also took the opportunity to call on the government to do something about the issue.
Ms Aitchison said the "wasteful, half-hearted solution" of a one-way overpass had created daily frustration for thousands of motorists each day.
In the lead-up to the March state election, Ms Aitchison and Labor did not make a commitment to fixing the problem.
Ms Aitchison said at the time she would not make a commitment until she had received the results of the Freedom of Information request, which arrived after the election.
"What I have read has only confirmed my earlier concern that the one-way overpass was always a Bandaid solution," Ms Aitchison said in parliament.
"Reports from RMS indicate that the upgrade failed within six months of opening to traffic."
RMS said that turning patterns at the roundabout had significantly changed after completion of the original modelling including a large increase of traffic out of Maitland CBD.
"It should be noted that the modelling was completed prior to the funding of the Hunter Expressway project, which had a significant impact on travel patterns in the area," the document said.
The documents also mentioned that motorists were using the "rat-run" through Maitland Park and included a traffic survey taken in the area before April 2017.
During the four hour survey period, 227 vehicles chose to "rat-run" - most of which were during the afternoon peak when the queue extended back to Louth Park Road.
A vast majority (170) used the u-turn facility on Cessnock Road to travel back through the roundabout, while the remainder continued down Cessnock Road.
Ms Aitchison said this was despite a childcare centre, sporting facilities, the local swimming pool and war memorials being located within the park precinct.
RMS has since committed to installing traffic lights at the eastbound approach to the roundabout as a temporary fix, after completing an investigation.
The preferred option of the investigation included closing the Walker Street exit to Maitland Park, but RMS said "closing this would result in an increase in traffic flows at the Louth Park Road intersection".
It also considered metering on both the north and west legs of the roundabout, "but neither option was sufficient to address the issue satisfactorily".
The government body also mentioned a one way system through Maitland Park and traffic lights at the intersection of the New England Highway-Louth Park Road intersection as options.
RMS did not respond to questions about those two proposals, but said work on the traffic lights would start in June while further traffic management changes were developed.
"This first stage of work will provide traffic flow improvements in the short-term while design work continues," a spokesperson said.
Meanwhile, Ms Aitchison has invited the Minister for Transport and Roads Andrew Constance to "come to Maitland, see the problem and focus on a proper and adequate traffic solution".
"Maitland is the fastest growing city outside Sydney, with a growth rate of 25 per cent since the 2006 Australian Bureau of Statistics Census and now home to 80,000 residents," she said.
"Minister, come to Maitland, see the roundabout and please fix it."
Ms Aitchison has spoken to Mr Constance about the problem. A spokesperson for the Minister said he wasn't aware of the issue until then, but has since asked RMS to meet with Ms Aitchison.