Transmission Gully from the air is an impressive piece of roading infrastructure.
The snaking 27km, four-lane separated motorway among steep carved mountainsides and rolling hills is an engineering feat not to be underestimated.
I had the privilege of flying over Transmission Gully on Thursday during the morning of its opening to the public.
With Dennis Young, of Kāpiti Heliworx, at the controls, we set off from Kāpiti Coast Airport once some distant fog had burned itself off just after 8.30am.
Hovering over the Wainui Saddle, the steepest part of the $1.25 billion gully route, with cuts of up to 70m, the road was busy with a steady flow of vehicles of all shapes and sizes.
I was keen to see how heavier vehicles were finding the gradient and soon saw a southbound logging truck hauling its way up the saddle with ease.
Apparently, the saddle is like Ngaranga Gorge but twice as long.
There had been a lot of talking pre-opening about how heavier vehicles would cope with the gradient, or not, so it was pleasing to see it was okay.
The gully route has slow lanes at certain points for trucks so you can pass with ease, and there's a gravel arrester bed if vehicles get into trouble when going north down the saddle.
Some social media commentary from truckies was a bit of a mixed reaction, with some saying they would continue to take the former highway along the coast.
As we moved high to the side of the saddle we saw white markings on a grass track indicating a route where a new walking and mountain bike trail would be built in the not-too-distant future.
It will be an amazing trail, with absolutely stunning views, and will no doubt require a good level of fitness.
Close to the proposed trail, we saw a group of about a dozen wild goats roaming about.
With eyes back on the road we carried on south to check out the Te Ara a Toa bridge over Cannons Creek, which stands 60m above the stream.
As we swooped back towards the airport we took a detour to see how much traffic was on the former State Highway 1 Centennial Highway — there was hardly any.
In the afternoon, with a keen sense of anticipation, I drove on the gully road from Kāpiti to Wellington and back.
It was a joy to drive on and you get a real appreciation for the amount of work that has been put into this roading project.
More than 11 million cubic metres of earth, enough to fill 4400 Olympic swimming pools, has been moved, the largest volume of earthworks on a roading project in New Zealand.
What I enjoyed most was being able to drive at a consistent speed, generally 100kmh, along the new motorway, which was wide and felt safe.
And the journey times were certainly a lot quicker than along the former highway, leaving you feeling a lot more refreshed at your destination.
Quite a lot of the road is chip sealed, and looked a bit patchy in places, and a few stones pinged the car, but apparently, some of those areas were re-swept a day after the opening.
Coming down the saddle, on the way home, there was a great view of Kāpiti, but it's steep so it's important to go easy on the accelerator.
And you need to be extra alert at the southern end, at the Kenepuru interchange area at Linden, when the route joins the motorway to Wellington.