A grader called in by the New Zealand Transport Agency last week to clear snow scraped off or damaged several stretches of "rumble strip".
The white, raised road markings were laid along the sides of the highway earlier this year to alert drivers veering left off the road.
Now, many of the noise and vibration-inducing thermo-plastic bumps show up as white chips, scattered along the highway verges.
Agency operations manager for Otago and Southland Murray Clarke said yesterday the part of the motorway where snow-grading was carried out was a "high wear area".
"The damage to this area is no more than what we would have expected."
"Most of the damage was caused by a grader used to shift deep snow.
"Snow ploughs were lighter and the blade tended "to ride over things a bit more".
Although some bumps were missing, Mr Clarke believed motorists would still know when they crossed the line.
"We still believe it's well worthwhile putting rumble strips in that area, even though we acknowledge we will have to carry out a bit of repair from time to time."
The rumble strip costs about $4000 per linear kilometre to lay.
A Waitati resident, concerned at the cost, raised the issue with the Otago Daily Times.
"They cost a lot of money to put down and then they go and plough them up again."
The man, who who did not want to be named, believed the strips were useful on long, boring stretches of highway but that people did not tend to lose attention on the Northern Motorway.
Mr Clarke said the agency would decide at the end of the winter how much of the strips would be repaired.
"We'll do it on a case-by-case basis."
Contractors are putting more safety, wire-rope guard rail in place along the highway near the top of the Leith Saddle.
Mr Clarke said plans to realign and straighten the motorway on the south side of the saddle were "not on the horizon".
"We've done some investigation into it.
"Obviously, we'll monitor the crashes and things that happen there.
"At the moment, there are higher priority jobs."
