Northland's main transport artery has been severed yet again but roading officials will decide today whether it is safe to re-open State Highway 1 on the Brynderwyn Hills.

The main road link to Northland was closed because of an underslip on the southern side of the Brynderwyns on Sunday after heavy rain. The underslip, about 20m long in the northbound lane, had fallen away leaving an 8m drop to the ground below.

Officials initially thought the highway would remain closed until the end of the week but after an inspection yesterday thought it could possibly be opened to light vehicles later today.

If experts give the all clear, one lane will be re-opened to motorcycles, cars and light commercial vehicles only. Traffic management will be in place to control north and south bound traffic, and the speed will be reduced temporarily to 30km/h.


NZ Transport Agency regional journey manager Jacqui Hori-Hoult said excavations began yesterday but because of the location and size of the underslip, it would be too risky to re-open the Brynderwyns to heavy vehicles until the Transport Agency has completed full repairs.

"Unlike the underslip on SH1 at Kawakawa last week, there is no room on the Brynderwyns to build a detour route around the collapsed section of road," Ms Hori-Hoult said.

"We will have to repair the underslip itself before we can re-open the highway."

"We are aware of the importance of this section of highway as the main road link between Northland and Auckland.

"Everything will be done to have it repaired as quickly as possible, but it will only be re-opened when we are completely satisfied it is safe for people to use."

The latest closure comes a week after SH1 was shut south of Kawakawa due to a massive slip. A temporary bypass around the site has now been opened.

Ms Hori-Hoult said a close eye was being kept on major roads in the region with significant cracks identified just south of Maromaku and in the Maungataniwha Ranges near Mangamuka.

Speed limits had been reduced in those areas and geotechnicians were testing in the areas to see if there was any more movement.


Traffic including freight transport now face new detours on the main route into the region with north-bound motorists being asked to use SH12 through Paparoa and Oakleigh and south-bound via Waipu and Mangawhai.

Northland Civil Defence Emergency Management spokesman Graeme MacDonald said the detours could add up to 45 minutes to journeys and care and consideration would be needed.

Given they could be used for a number of days, authorities would make regular checks to ensure the alternate roads were actively managed and coping with the additional traffic.

"One positive is that at this stage, the showery conditions forecast for the next few days are not expected to cause any new weather-related problems," Mr MacDonald said.

Work on a slip on SH12 at Kaihu would take weeks with contractors having to build a rock wall and building the road back up again.

Police would be patrolling the detours and urged drivers to take care on the roads which were narrow and winding.

Inspector Murray Hodson said it would take motorists longer to get to their destination and urged them to be patient and drive to the conditions.

He encouraged motorists to report cases of poor driving by calling *555.