UNH researchers say roads need to be thicker to withstand climate change

The move would extend their life cycle and keep future costs down
Crack textured asphalt road background.

Researchers at the University of New Hampshire say roads that are increasingly vulnerable to climate change should be constructed with thicker asphalt in order to extend their life cycle and keep future costs down.

“It’s all about being strategic with the maintenance of our highways and byways,” said Jo Sias, professor of civil and environmental engineering at UNH. “Just like a regular oil change can help extend the life of a car, our research shows regular maintenance, like increasing the asphalt-layer thickness of some roads, can help protect them from further damage related to climate change.”

In their study, recently published in the journal Transportation Research Record, the researchers looked at the seasonal and long-term effects on pavement life, like climate-change-induced temperature rise and higher groundwater levels due to sea level rise and heavy rains. They looked at the changes in season length, increased flooding, average temperatures, projected temperatures and resilience based on those temperatures.

As global temperatures continue to rise, road conditions will shift. The winter pavement season is projected to end by mid-century, replaced by a longer fall season. Pavement damage, now seen mostly in the spring and summer, is projected to be more distributed throughout the entire year. Based on their analysis that looked at the wear and tear of roads, the researchers determined that a 7% to 32% increase in the asphalt-layer thickness might be the best way to maintain the service ability of some roads.

“For agencies and towns, it is a balancing act to repair roads, so we’re trying to find some reasonable action that can be taken now to help manage their infrastructure,” said Sias. “If global warming continues, then we know temperatures will rise and pavement doesn’t respond well to increased temperatures. The hope is to find some answers now so cities and towns can plan for the future.”

Other expense increases

The researchers said they recognize that increasing the asphalt thickness to certain roads can be an added expense for cities and towns, but they point to considerable future savings of between 40% and 50% if done now rather than later.

Along with the rise in cost of materials, there could also be other expense increases down the road, including project planning, design and construction. Environmental impacts could also be costly, with rough pavements adding to increased greenhouse gas production, which has the potential to accelerate climate change.

While the study looked specifically at the impact of the changing pavement seasons and the increase in temperatures and flooding at a site in coastal New Hampshire, the researchers say the approach has the potential to be applied to most roads and highways both nationally and globally. The adaptation approach, of calculating the pavement layer thickness required to maintain a safe road reliability level, could provide the guidance to address the effects of rising temperatures and changing seasons on those byways.

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