Why pavement mapping is important for building resilience in New Zealand's road infrastructure

What is pavement mapping? 

Pavement mapping is a non-destructive and non-invasive technique that scans road surfaces using GPR (Ground penetrating radar) technology that sends a radar wave through the layers of asphalt to evaluate the condition of the pavement.  

How is this useful? 

The ground-penetrating radar can capture detailed information about the subsurface layers of the pavement, which can provide evidence for engineers planning road maintenance or upgrades. By understanding the thickness of the road, engineers can decide whether it’s possible to use less invasive techniques such as milling and filling. This involves shaving the top layers of asphalt, to reshape and upgrade road surfaces, without hitting the subgrade, which can significantly weaken the existing road. It also supplies evidence to support where full reconstruction work is necessary. 

The above GPR data shows asphalt over granular, above the subgrade. The asphalt-granular and granular-subgrade boundaries are clearly visible. (Image Source: Sensor and Software)

What are the benefits of using pavement mapping in project planning? 

• Accuracy

  GPR provides highly accurate and detailed information about the pavement structure, enabling precise decision-making. 

• Non-Destructive

  It does not require destructive sampling, preserving the integrity of the road and reducing costs associated with traditional assessment methods. 

• Cost-Efficiency

  By identifying issues early, engineers can plan cost-effective maintenance strategies, extending the lifespan of roads and reducing repair expenses. 

• Data Integration

  The data collected can be easily integrated into GIS and asset management systems, streamlining decision-making processes. 

What else can pavement mapping detect?  

Pavement mapping can also detect shallow utilities and weaknesses throughout the road corridor, identifying voids that can develop into larger sinkholes, like the ones that opened earlier this year in Auckland. Most voids start from stormwater that becomes trapped under the road and slowly erodes the earth.  

Sinkhole that opened in St Georges Bay Road in 2023 from a sewer pipe collapse (Image source: RNZ)

Why is pavement mapping so important now, and as we look to the future? 

The main causes of road deterioration and sinkholes are the density of traffic flow and excessive water erosion under the surface. A current issue throughout the world is our rising population and rising temperatures, both of which lead to heavier road use and erratic weather events. 

Earlier this year, Roads Australia (RA) submitted to the Federal Parliament’s Inquiry into the Implications of Severe Weather Events on the National Regional, Rural and Remote Road Network, calling for a more strategic approach to road maintenance.  

RA CEO, Michael Kilgariff, said a spate of natural disasters over recent times highlights the need for greater focus on the resilience of road infrastructure. The current roads were designed using data from historic weather patterns with the intention of them lasting 100-year lifespans, however with the rapid changes in our climate, this is no longer the case. Throughout 2022-23 there has been a 2x rise in pothole occurrences, which has fuelled Roads Australia's governmental submission calling for improved pavement technologies that can not only improve resilience but sustainability.  

Whereas in the US, they have already instigated a proactive response after the United States Geological Survey (USGS) estimated that sinkhole damages cost on average at least $300 million annually. In light of this revelation, the Committee on Natural Resources passed the Sinkhole Mapping Act of 2019. This directed USGS to establish a program to proactively map high-risk areas to establish a comprehensive database that could be revised and updated. The directive aims for these maps and other relevant information to be used by community planners to ensure effective design and allocation of resources throughout infrastructure projects.  

In New Zealand, It is a well-known fact that we have issues with aging infrastructure and the road to amending this is long and costly. So, we need to be smart.   

As reported by 1News, due to climate change and pollution, the stormwater that collects under the roads is acidic, corroding more of our infrastructure each year. Couple this with severe weather events becoming more frequent, as Waka Kotahi recorded seven 'significant' events between 2018 and 2021- compared with just two significant events in the four years prior. To put this into perspective, ’significant’ means they cost between $15 and $50 million in repairs per event.  

As a consequence, with continued climate shifts it is likely that heavy rain events will continue to occur. We need to start moving proactively rather than reactively. As the media reports on the mounting issues and costly backlog of required road repairs around the country, efficiently allocating resources and prioritising high-risk areas has never been more important. 

Reveal at work with our vehicle-mounted DXG antenna series array.

What we’re doing about it 

We’re heading to the Future Roads Summit later this year to connect with delegates, chief executives, and government leaders to discuss updates on the latest roading projects. Exploring opportunities to educate the industry on proactively mapping pavements throughout urban areas, where we can identify these risk areas prior to damage occurring, significantly reducing the risk of extensive disruption to the public and the economy.  

If you want to learn how pavement mapping can support your project or region reach out to the Reveal team for a free consultation.  

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