Regular users of the Auckland Harbour Bridge may have noticed a slighter different colour, texture and sound to the centre lanes over the past week.
The NZ Transport Agency’s motorway maintenance team has been giving the road surface a new lease on life and improving its skid resistance by removing a very thin layer off the surface.
The colour of those lanes is now slightly lighter and the new texture means road users may also notice it sounds different too.
The Auckland Motorway Alliance’s Director Steve Mutton says a special machine has been micro milling to create minor grooves in the road and expose high friction surfaces of the existing stones in the pavement to improve its texture.
“This improves the skid resistance and therefore the safety of the road surface.”
“The NZ Transport Agency has strict policies on the skid conditions of its highways. Each year every piece of highway surface is tested to check whether it meets thresholds for skid resistance. Sections that fall below the thresholds are then prioritised for maintenance repairs.”
The centre lanes of the Auckland Harbour Bridge are surfaced in an older material that is in good general condition but lacks the required surface texture.
Micro milling has been a cost effective way of refreshing the surface and ensuring it meets the necessary texture and grip levels.
“It’s the first time this particular micro milling machine has been used on the NZ Transport Agency’s network. Until now the full depth of the road surface had to be replaced, which is a comparatively expensive exercise. Micro milling removes as little as 2mm from the surface to modify its properties.”
One of the other benefits of the micro milling is that the lane markings will now be more clearly visible in wet weather and poor light conditions.
“We have opted to leave the existing line marking and micro mill on either side of the lines, which creates a raised surface that will now be more visible when the road’s wet.”
The previous surface had lasted approximately eight years before it fell below the safety threshold and it’s expected it’ll be another five years before it needs more work.