Auckland motorists are being warned that exceptionally high tides on the Manukau and Waitemata Harbours later this week could cause flooding to low-lying sections of the city's motorway network.
High tides of up to 3.6m, about half a metre higher than normal, are expected between Tuesday 27 September and Sunday 2 October.
The NZ Transport Agency (NZTA) said the tides will be at their peak on Thursday and Friday morning when commuter traffic volumes will be high.
"There could be some flooding, but the tides don't pose a significant risk to the safe operation of Auckland's motorways," said the NZTA's State Highways Manager for Auckland and Northland, Tommy Parker.
The area most at risk is the section of the highway and adjoining cycleway on the Northwestern Motorway (State Highway 16) causeway between the Patiki Road Interchange and the Rosebank Road Bridges.
"When the tides peak the cycleway will definitely be underwater, and we are asking cyclists to try to avoid using it 1.5 hours either side of high tide," said Mr Parker.
"Drivers should also cross the causeway with more care, and if necessary we will divert them on to arterial roads so that they can continue their journeys safely."
As part of its project to complete the Western Ring Route motorway alternative to SH1, the NZTA is planning to raise the causeway by 1.5 metres and increase its width to provide extra lanes.
For more information on tide times, alternative routes or planned detours and closures please contact NZTA Auckland Motorways on 09 5200 200, email firstname.lastname@example.org or visit www.aucklandmotorways.com