$415 million electricity supply improvements likely to cause delays for city-bound motorists.
Buses normally allocated their own lane along one of Auckland's heaviest commuter routes will have to vie for space with cars during months of post-Christmas roadworks in Fanshawe St.
The city-bound bus lane between the Northern Motorway and Nelson St will be opened to general traffic while the road is narrowed between next week and March to make way for a $415 million electricity supply upgrade for Auckland and Northland.
Although two lanes will remain available to traffic from December 27, commuters from the North Shore will be urged to avoid delays by using the motorway's Cook St or Grafton Gully exits to reach downtown Auckland.
Electricity grid operator Transpower, which is laying a high-voltage supply line from Pakuranga to Albany via the Northern Motorway, will also take advantage of lighter summer traffic to close both city-bound lanes of Waipuna Bridge in east Auckland until January 13.
Commuters who normally rely on that link to the Auckland isthmus from Pakuranga and Botany will have to use nearby Panmure Bridge or the Highbrook approach to the Southern Motorway.
Waipuna Bridge's eastbound lanes will remain open even though cable ducts have to be installed on each side of it.
But commuters heading home across the harbour bridge between Boxing Day and January 6 could face extra delays when the Transport Agency closes the northbound clip-on lanes and the Curran St on-ramp for annual resurfacing.
Transpower's summer construction push will also affect traffic on Westhaven Drive, including those towing boats to or from the marina next to the bridge.
Dec 26 to Jan 6
Two northbound clip-on lanes to harbour bridge and Curran St on-ramp to close for resurfacing.
Dec 27 to Mar
One city-bound traffic lane in Fanshawe St to close - cars to be allowed in bus lane.
Dec 27 to Jan 13
Both city-bound traffic lanes to close on Waipuna Bridge from Pakuranga to Auckland isthmus.