The study looked at seven new bypasses constructed between 2009 and 2016 – Auckland's Northern Gateway, Tauranga’s Eastern Link, Wellington’s Mackays to Peka Peka Expressway, the Waikato Expressway, and bypasses in Cambridge, Ruby Bay, and East Taupō.
WSP compared before and after crash statistics in ‘areas of interest’ using data in Waka Kotahi’s Crash Analysis System (CAS). The areas of interest included the new bypasses, the old roads and associated intersections.
Construction of the new bypasses was found to have reduced crashes across all areas of interest by 22.5 percent. This resulted in a 29 percent reduction in minor injuries across all sites, and a 37 percent reduction in death and serious injuries (DSI’s).
The drop in the number of crashes was observed across a range of crash types, including head-on collisions, losing control, overtaking, rear-ending, pedestrian vs. vehicles, and turning at crossings.
With DSI’s, the most notable reduction was a 57 percent decrease in the bend-lost control / head-on crash type, followed by a 40 percent reduction in the straight - lost control / head-on crash type, and a 35 percent reduction in the crossing / turning crash type.
Data from 2020-2022 was mostly excluded from WSP’s analysis because COVID-19 restricted travel and resulted in fewer crashes during those years.
WSP principal road safety engineer Mark Newsome says new road bypasses reduce crash statistics for several reasons. One of the main factors is that they provide alternative high-quality routes for motorists - separating through and local traffic and making our townships more appealing places to walk or cycle.
"This can lead to a decrease in the likelihood of accidents happening, as there's fewer opportunities for collisions. New bypasses also incorporate design features that improve safety by removing out of context curves, providing road safety barriers and reducing impact speeds and collision angles at intersections. These features can help reduce the risk of accidents, especially at intersections or other areas where the road layout may be more complex."
AA Research Foundation manager Dylan Thomsen says having real world figures around the safety impact of a range of new stretches of highway will have a lot of value for future planning and projects.
“The findings highlight how it’s not just the new road where there is significantly less trauma but the old road as well – which is really important when so many highways in New Zealand are also the main road of a town.
“There’s no question that we need to be making our transport more sustainable and getting more zero emissions vehicles into our fleet, but building or upgrading roads is still a key part of the mix in helping achieve the country's road safety goals.”
For more information and to read the study’s full findings, visit the AA website.
