An isolated rock spill has heralded the opening of the Manawatu Gorge to two-way traffic.
The New Zealand Transport Agency said the rock fall happened a few hundred metres down the road just as they were getting ready to open the gorge to two lanes in "a classic case of Murphy's Law".
"We've ensured that the hillside is secure, but we'll need to fix the damage which may mean briefly shutting the highway at a later date," said Palmerston North state highways manager David McGonigal.
However despite the setback motorists in the area are breathing a sigh of relief as the gorge road reopened to two lanes of traffic for the first time in a year.
The stretch of State Highway 3 which connects the Manawatu to the Wairarapa was closed after a large slip on August 6 last year.
It was followed by other slips, which prevented the road from being cleared.
Engineers have spent months removing the earth and rocks which cascaded down the gorge and onto the road.
One lane of the road opened to traffic in August.
While the road opened today, one lane 'stop/go' controlled sections will still exist at two points, but restrictions have been lifted on vehicles travelling east from Ashhurst during the day.
"This is the first time since the gorge closed last year that we've been able to get two lanes of traffic through the slip site," said NZTA Palmerston North state highways manager David McGonigal.
"While it's not two lanes the whole way through, it's a huge leap forward and a sign that the end is near.
"It's been achieved ahead of schedule by a very dedicated crew, and they've earned a long holiday when all this is over."
McGonigal said that while the gorge can now accommodate all the traffic that has previously been diverted onto the alternative routes, there may be minor closures in coming weeks to enable further work to be completed.
"Having two lanes up and running means that everyone who has been patiently winding their way through the alternative routes can now return to the Manawatu Gorge, and save themselves time, petrol and peace of mind while they're at it," he said.
However, he urged motorists to keep their eyes peeled for signs, as restrictions or closures could still happen at short notice depending on the work required on site and weather conditions.
The New Zealand Transport Agency are still carrying out work on the new section of highway through the gorge, including rockfall netting to protect motorists from debris spills.
While this is being carried out a 30km/h speed restriction will be in place, and motorists are asked to expect some minor disruptions.
Two small sections will remain restricted to one lane - at the Woodville end of the slip where crews are still at work, and at approximately 500m towards further towards Woodville following damage caused by an isolated rock spill.