Green Roads

Project Client: Tuhoe Trust
Project Year: 2016 to 2020
Contact: Matt Sharp, Research Manager Transport

In 2016 the Tūhoe Trust commissioned WSP Research to investigate potential options for the resurfacing and maintenance of the section of State Highway 38, which is largely unsealed as it runs through Te Urewera.

The road is essential for maintaining connectivity and services to an isolated rural community and for the development of the tourism industry in Te Urewera. Eschewing traditional construction methods, the Tūhoe Trust challenged WSP to innovate an environmentally-friendly and sustainable approach in keeping with the values of their people.

The world-first solution is at the cutting-edge of innovative sustainability and has proved to be successful in field trials.
It uses a tree resin, a natural by-product of the wood pulping process used in pulp and paper manufacturing, which is used in a novel way to bind the gravel and keep it in place.

The result is a solution that suppresses dust – an issue on gravel roads as it obscures visibility – with waterproofing attributes that reduces the occurrence of potholes and corrugations.

Innovative Asphalt - Low Noise and Long-Life

Project Client: NZ Transport Agency
Project Year: 2016-17
Contact: Phil Herrington, Senior Research Scientist

Although the safety and noise-reduction properties of open graded porous asphalt (OGPA) are well documented, binder oxidation is a major problem and is the principal factor governing the ultimate life of porous asphalt. The result is a rough, uneven riding surface. In New Zealand, the average lifetime of OGPA is very short, in many cases only seven or eight years.

WSP collaborated to produce a long-life (30 years plus) surfacing material with low maintenance requirements and low noise generation. Trials on state highways, and the Auckland Harbour Bridge were successful and the product is now in use where quality low-noise roads are required.

NZTA estimates that their annual maintenance budget for low noise pavements will reduce to 1/6 of current levels where the innovative asphalt is used.

WSP put NZ on the world stage by undertaking this research as part of a larger international research programme conducted under the auspices of the OECD. The Dutch laid their first epoxy porous asphalt trial after visiting New Zealand to see how it was done, and the American Federal Highways Administration (and OECD partner) reopened research on the topic after having heard about the New Zealand approach.

Sharing The Road

Project Client: NZ Transport Agency
Project Years: 2016 - 2019
Contact: Jared Thomas, Technical Principal-Behavioural Science

At WSP’s Research & Innovation centre in Petone, a world-first instrumented bicycle is helping provide a better understanding of the factors affecting cyclists’ experiences on New Zealand’s roads.

A team of behavioural scientists, sustainable transport experts and instrumentation engineers have undertaken innovative research for Waka Kotahi – the NZ Transport Agency, providing them with a solid scientific basis to inform their goal of improving levels of cycling throughout the country.

Jared Thomas is a leading expert in the research and design of spaces for vulnerable road users. He says that although it’s currently the most repressed mode of transport, there is potential for cycling to become the largest demand growth area.

Figures support this. The Ministry of Transport Household Travel Survey shows that although 31% of New Zealanders aged over 15 have cycled in the past year, less than 2% of trips are made by bike. A key target group for improving uptake is the ‘interested but concerned’ 20-30% of people who would like to cycle more, but are discouraged by safety concerns.

Jared’s research confirms that their concerns are justified in many cases, with most riders experiencing an uncomfortable interaction with a motor vehicle on their ride – typically one every 22 minutes.

“These incidents are from a vehicle overtaking too closely, but can also be from other cyclists overtaking closely. Another common example is a vehicle cutting them off at intersections or roundabouts, such as turning left in front of them or suddenly pulling out.”

Thoughtful, connected infrastructure design has a large part to play, particularly for less experienced cyclists, explains Jared; one bad element of the route will stop a rider from completing the whole journey.

Tension between cyclists and motorists is also an issue, but Jared acknowledges that while much is made of the animosity between drivers and cyclists, WSP’s ‘passing gap’ research demonstrates that most drivers do give cyclists an appropriate amount of space.

Rubberised Cycleways

Project Client: Ministry for the Environment
Project Year: 2015-2019
Contact: Matt Sharp, Research Manager Transport

Cycleways are big news right now, with many new urban and off-road projects either installed or underway across the country. These cycleways could become even more attractive for users thanks to an innovative pavement material delivered by WSP Research.

Our pavement materials and behavioural sciences teams are in the final phase of a three-year project to trial an exciting alternative pavement material made from rubberised asphalt made from recycled tyres.

The asphalt is mixed with bitumen that has devulcanised tyre-rubber added to it, resulting in numerous benefits including increased resistance to fatigue and oxidation – factors that traditionally undermine asphalt pavement durability over time.

Each year New Zealand creates five million waste tyres, so finding a way to recycle tyres is a highly sustainable approach and takes care of an abundant waste material that would otherwise languish in landfills.

Finding a way to recycle tyres is a highly sustainable approach and takes care of an abundant waste material that would otherwise languish in landfills.

Since the rubberised asphalt surface was laid down, our behavioural scientists have been collecting data by way of intercept surveys to capture feedback from the local community. The response so far has been extremely positive.

We’ve also been using an instrumented bike as a quantitative tool to demonstrate that not only is ride quality for the rubberised pavement comparable to that for standard asphalts, it is also far superior to the ride quality experienced on chip seal and gravel alternatives. Our researchers are currently quantifying the levels of chemical compounds that are emitted as gases under manufacturing conditions with assistance from AsureQuality. We’re hoping to confirm that there will be no unintended negative side-effects from using rubber waste in this useful way.


Wendy Turvey
National Manager Research (Lower Hutt)
New Zealand
Louise Malcolm
Research Manager People (Human Factors and Social Sciences)
New Zealand
Sheldon Bruce
Technical Principal - Concrete Technology
New Zealand