Published Tuesday, 17 January 2012
Over 20 cases have been reported of vehicles travelling towards oncoming traffic on the road between the M1 motorway and Ballygawley.
It opened in November 2010 and there has been one accident involving an injury so far, which the police are investigating.
New signs were put up at all junctions on the A4 last September to raise awareness of which direction to drive.
The Department for Regional Development is now going a step further by installing more signs, white lining and cones in a bid to stop future incidents.
"This is an extremely serious matter," said DRD minister Danny Kennedy.
"Despite additional 'No Entry' and 'Left Turn Only,' signage, some drivers are continuing to ignore the signs and are travelling the A4 in the wrong direction.
"These actions are highly dangerous and could have grave consequences."
The A4 was one of the most notorious stretches of road in the region but the number of crashes has been reduced since the reopening.
It currently carries around 20,000 vehicles per day at its eastern end, near the M1, and around 16,000 vehicles per day at Ballygawley.
Mr Kennedy urged motorists to take care on the carriageway.
"It is absolutely essential drivers pay attention to the roads signage at junctions when joining the new A4," the Ulster Unionist politician continued.
"Drivers must not rely on previous journey habits in the vicinity the A4 before the new road improvements.
"Nor should they rely on sat nav's that have not been updated to reflect the new road layout.
"The simple rule to remember is: right turns onto the dual carriageway, are prohibited at all junctions."
The Roads Service said it will continue to monitor the situation.