Two of the country's fastest roads are actually saving lives.

No one has died on either the Cambridge section of the Waikato Expressway, or the SH2 Tauranga Eastern Link Toll Road, since they opened just over two years ago, figures released to Stuff show.

Waikato Road Policing Team Leader Rupert Friend said he wasn't surprised by the lack of crashes because roads rated at 110kmh were required to have side and median barriers. 

"From a road policing perspective if we could build 80,000 km of the road like that in New Zealand I would be a happy camper," he said.

The increased speed limit of 110kmh was implemented on December 11, 2017, on both sections of road.

Since then, until October 2019, there have been no fatal crashes at all on the Cambridge section, between Tamahere and Karapiro, with one serious crash, two minor crashes, 17 non-injury crashes reported.

"Because if something goes wrong everybody is going in the same direction and therefore it's highly unlikely that anybody is going to come to an absolute sudden stop which is where the deaths happen.

On the Tauranga Eastern Link Toll Road - there have been three crashes reported - with one being minor injuries and the other two were non-injury crashes.  

The type of vehicles involved in those crashes have largely been cars, vans and SUVs.

Friend said the Cambridge section was "about as safe an engineered road we can have".

"Because if something goes wrong everybody is going in the same direction and therefore it's highly unlikely that anybody is going to come to an absolute sudden stop which is where the deaths happen.

"It's the rate of deceleration that kills people whether that is hitting a concrete wall, a truck, a car coming the other way or a tree that expressway excludes you to get to anything like that." 

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He said the wire barriers were designed to bounce you back onto the road after absorbing a lot of the energy, therefore slowing you down.

While he'd love to see all roads in New Zealand designed in the same way, he acknowledged that wasn't possible.

"But it's physically not going to happen, so the risk is around our roads on which people are separated by a narrow white line and they're doing 100kmh that is where the speed is more concerning."

He said that deviating by five or 10 kilometres on 110km doesn't have a lot of impact whereas speeding on a road with no median barrier like on SH1, after the Expressway ends at Karapiro, was hugely dangerous. 

"Taking someone's speed from 104km to 103km reduces the likelihood of fatality in a crash by four per cent. So if you actually decrease their speed by seven or eight kilometres down from 110km to sitting at 100km you actually decrease that likelihood of fatality hugely if something goes wrong." 

It also means officers can focus resource on the more dangerous pieces of road. 

"I think we've had one serious injury but it has dramatically reduced from what it was." 

"Our three highest risk roads in the district and our top priority are SH1 Karapiro, the triangle at Matamata which is SH29, SH27 and SH24 and SH25 to SH25a up and over the Kopu Hikuai - so our highways staff are told that it's non-negotiable you will be there every day."

Crashes had also deceased on the Expressway from Te Rapa to Taupiri. Although it's not engineered to the same level as the other two roads, as it doesn't have a left-hand barrier the entire way. 

"I think we've had one serious injury but it has dramatically reduced from what it was." 

He believes the finished Huntly section will also see a reduction in serious crashes. 

"That Huntly stretch is one of our most dangerous roads around."

An NZTA spokesperson said the speed limit would only be increased to 110kmh on roads which could support higher travel speeds without compromising safety. 

That included having standards such as two lanes in each direction, a median barrier, no significant curves, and no direct access to neighbouring properties. 

"At present only a few state highways are likely to meet these standards."

The 110 km/h speed limit requires separate approval and bylaw. The decision on making a 110 kmh speed limit bylaw lies with the relevant road controlling authority along with consultation. 

For the consultation of the SH1 and SH2 sections to be increased to 110km NZTA received almost 11,500 submissions from the public and stakeholders with 73 percent of the submissions in favour of increasing the speed limit on the two roads.