Building a brand-new stretch of highway can mean people and freight get places more quickly, it can make cities and towns more pleasant by removing traffic and can also make the transport network more resilient if extreme circumstances close a route.
But reducing harm from crashes is often the main benefit sited for promoting road building projects. A recent study from the AA Research Foundation investigated just how much new road can improve safety.
The study analysed crash numbers following the construction of seven new stretches of highway across the country since 2009.
The key insight revealed that new roads delivered (on average) a 37% reduction in overall deaths and serious injuries. Minor injuries fell about 30%.
| Overall reduction in deaths and serious injuries following the opening of new highways (excluding Covid-affected years of 2020-2021) | % reduction |
| Northern Gateway (Auckland) | 43.5% |
| Tauranga Eastern Link (Bay of Plenty) | 20.5% |
| Te Rapa and Ngāruawāhia (Waikato) | 55.4% |
| Cambridge (Waikato) | 33.3% |
| East Taupō | 4.5% |
| Mackays to Peka Peka (Kāpiti) | 90% |
| Ruby Bay (Tasman) | 40% |
| Total across all sites | 37.3% |
The ‘overall’ aspect is important, as this research took a different approach to traditional comparisons – we didn’t just look at how many crashes there were on the new road compared to the old road.
Instead, this research looked at how many crashes originally happened on the old road and then compared that number to how many crashes occurred on both the new and old road combined once there were two of them.
For example, the Mackays to Peka Peka route had five serious injuries in four years after it opened but only one of those was on the new expressway; the other four were on the old road. Previously that old road had experienced two deaths and 11 serious injuries in four years.
“This study not only confirmed that new roads have much lower crash rates but also that the original roads tend to experience a significant crash reduction as well. A win-win,” says AA Research Foundation manager Dylan Thomsen.
“The improved safety benefits for the old roads is really useful to include, as many stretches of highway are also still the main road of a town. With the push to make towns and cities more ‘liveable’ and more inviting for pedestrians and cyclists, removing highway traffic from towns fits well with aims to improve safety, make the environment more pleasant for people and improve air quality and emissions.”
Highways with median barriers are the safest option for new roads.
The researchers believe it’s the first study of its kind in New Zealand to put real-world figures on the scale of crash reductions likely to be created by new highways and bypasses.
Much of New Zealand’s state highway network was built at a time when traffic volumes were lower, and these roads have potentially fatal hazards like power poles, trees and ditches close to the edge of the road, as well as an absence of barriers separating oncoming traffic.
“When you look at countries with better road safety records than New Zealand, they tend to have much higher quality highway networks than we do,” Dylan says.
“Another thing that stood out from the research was that the two routes with the lowest safety improvements compared to their surrounding area – East Taupō and Ruby Bay – were both places where the new highway did not have a median barrier for its entire length.
“It is a reminder that when we are building a new highway it should have all the safety features we know make a huge difference. The research also shows that, even when a new highway is built, improvements made to the old road will also continue to reduce risks.”
What do you think? Have you noticed improvements in the roads and highways near you? Share your thoughts!
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