Police are advising motorists to keep left, after a rash of recent complaints about vehicles weaving over the centre line.
Several infringement notices have been issued in the past fortnight to drivers who have drifted into the right lane, Constable Greg Nolet said.
Police recently forbade a tourist to drive after a following commercial driver reported the rental car had crossed the centre line between 50 and 100 times on State Highway 6 between Cromwell and Wanaka, Const Nolet said.
The driver was then observed by police for a minute, during which time the vehicle crossed the centre line twice.
"You could only put it down to total inexperience," Const Nolet said.
Other recent complaints have included overtaking on blind corners and slow-travelling vehicles.
