University of Surrey tests geothermal system to prevent potholes

Researchers at the University of Surrey have begun a trial that uses ground-source heating and cooling to regulate road temperatures and reduce pothole formation. The Thermo-active Roads for Heat Harvesting and Pavement Temperature Regulation project embeds a network of heat-exchange pipes beneath the asphalt and underlying layers. During summer, circulating water absorbs heat from the road surface and transfers it to a 100-meter-deep borehole for underground storage. In winter, the stored heat is circulated back through the pipes to warm the pavement, preventing ice formation and reducing the freeze-thaw cycles that cause cracking.

Installation started in the Senate House parking lot on the university's Stag Hill campus, with the first phase underway and a second phase beginning in mid-August 2026. The system uses standard plastic pipework and water circulation pumps, materials the researchers describe as mature and readily available. Underground sensors will monitor pavement temperatures over several years to assess how effectively the system regulates thermal conditions.

Project lead Dr. Benyi Cao, a senior lecturer in geotechnical engineering and Royal Academy of Engineering research fellow, said the goal is to prevent potholes before they form rather than repairing them afterward. Dr. Nikolas Makasis, lecturer in civil engineering and co-investigator, said the trial will provide real-world evidence of how geothermal road systems perform outside laboratory settings. Previous studies in Europe and the United States have explored similar concepts, but the Surrey project aims to deliver detailed performance data under U.K. conditions.

The research team will also measure air temperatures above the test section to investigate whether cooler pavement surfaces could reduce surrounding air temperatures during extreme heat events. If results are promising, the researchers say road authorities would have evidence to deploy the technology for longer-lasting roads, lower maintenance costs, and greater climate resilience. The project is funded by the Royal Academy of Engineering and supported by the University of Surrey.

Potholes are a persistent problem in the U.K., causing safety hazards, journey disruption, and high repair costs. Freeze-thaw cycles, where water enters cracks, freezes, expands, and widens the damage, are a primary driver of pavement deterioration. By maintaining more stable road temperatures year-round, the geothermal approach targets this mechanism directly. The trial's multi-year monitoring period is designed to capture seasonal variations and long-term system performance.

The concept of thermo-active pavements has been studied for decades, but practical deployment has been limited by a lack of full-scale, long-term field data in temperate climates. The Surrey installation represents a step toward closing that evidence gap. Researchers emphasize that the technology uses conventional civil engineering components, which could simplify adoption if the trial demonstrates clear benefits.

Outcomes from the trial will inform future decisions about scaling the technology to public highways. The research team plans to publish findings as data accumulates over the monitoring period. Cost-effectiveness, durability of the pipe network under traffic loading, and energy balance across seasons remain key questions to be answered by the ongoing measurements.