Japanese Road Repair Technology, Old and New
Discover how Japan remains at the forefront of road infrastructure and repair.
Japan’s expertise in road repair has been shaped by centuries of practice and a mountainous geography prone to natural disasters. From ancient highways to today’s complex network of nationwide expressways, methods have continually been refined to keep routes safe and reliable. Earthquakes, typhoons, and landslides have further honed repair techniques. Today, Japan uses both traditional methods and advanced technologies to support infrastructure development and reconstruction.
Expertise learned from disaster and recovery
Japan’s ability to respond swiftly to damaged infrastructure is the result of repeated experiences with catastrophe, including earthquakes, flooding and volcanoes. Japan’s reconstruction after World War II created a foundation for modern construction and road repair. Postwar rebuilding accelerated the adoption of mechanized equipment, new materials, and standardized methods. The 1995 Great Hanshin-Awaji Earthquake exposed the vulnerability of expressways and bridges. It led to the reevaluation of standards for earthquake-resistant design, reshaping civil engineering nationwide.
The tragedy of the 1995 Great Hanshin-Awaji Earthquake which is thought to have killed at least 5,000 people helped to develop many of Japan’s infrastructure standards today.
The tragedy of the 1995 Great Hanshin-Awaji Earthquake which is thought to have killed at least 5,000 people helped to develop many of Japan’s infrastructure standards today.
The 2024 Noto Peninsula Earthquake showed the importance of reopening roads to secure rescue routes. Within 29 hours of the quake, key connections to city halls in the hardest-hit areas were cleared for passenger cars, and by 46 hours, large vehicles could also pass. This rapid road opening allowed emergency personnel to reach isolated communities within the critical 72-hour window for lifesaving operations. These are just some of the many experiences that have led to a culture of resilience in Japan’s roadwork. They continue to inform both traditional practices and the development of cutting-edge technologies.
Ancient techniques for today: The Do-nou method
A Japanese road innovation with deep historical roots is the do-nou method. Do-nou are sandbags, used in Japan since at least the fifth century. Small bags are filled with soil and stacked to fill potholes and reinforce the ground. The low-tech method requires minimal equipment, uses local materials, and can be carried out by community members with little training. The ubiquity of the sandbag allows it to be used in a variety of ways for road repair. Sandbags can hold down tarps, be stacked to create levees to protect against flooding, or even be used as markers to direct traffic around potholes. They are incredibly useful in any situation and can be found around most construction sites in Japan. In recent years, the do-nou method of road repair has been adopted in rural areas of Africa and other regions with underdeveloped roads.
Hand-filled sandbags, or do-nou, have been used throughout history in a variety of ways for road repair, even for things as simple as demarcating areas.
Hand-filled sandbags, or do-nou, have been used throughout history in a variety of ways for road repair, even for things as simple as demarcating areas.
The CAE Stabilizer method: Sustainable road building
Modern Japanese innovation also emphasizes sustainability and resource efficiency. First used in Japan in the 1980s, the Cement Asphalt Emulsion (CAE) Stabilizer method strengthens roadbeds by mixing cement and asphalt emulsion into the underlying soil. In this process, cement hardens within the soil particles, providing rigidity, while the asphalt emulsion coats and binds them, adding flexibility. The result is a foundation that is both strong and resistant to cracking under heavy loads or temperature changes. Because the existing soil is reinforced rather than replaced, this method allows old road materials to be recycled on site, reducing the need to excavate, transport, and import large volumes of new material—an approach that is both cost-effective and logistically efficient.
Sakai Heavy Industries pioneered the use of the CAE Stabilizer, now used in many parts of the world. Here, the Sakai PM500 is recycling the existing pavement on-site by blending it with stabilizing agents to form a new, durable road foundation. (Photo courtesy of TOA ROAD CORPORATION)
Sakai Heavy Industries pioneered the use of the CAE Stabilizer, now used in many parts of the world. Here, the Sakai PM500 is recycling the existing pavement on-site by blending it with stabilizing agents to form a new, durable road foundation. (Photo courtesy of TOA ROAD CORPORATION)
Fast-setting asphalt for emergency repairs and recovery
In addition to contributing to long-lasting infrastructure, Japanese roadwork techniques can be useful in critical, rapid-response situations. Disasters or conflict often leave roads impassable, slowing relief efforts. Conventional asphalt cannot be applied in wet conditions and typically requires six to twelve hours to harden before it can be used. Japanese-developed all-weather, quick-setting asphalt that hardens in under an hour addresses this challenge, allowing roads to reopen rapidly after damage. It can even be set in standing water and requires no heavy equipment.
Being able to fix roads with minimum equipment can be critical in emergency situations.
Being able to fix roads with minimum equipment can be critical in emergency situations.
Potholes may seem innocuous, but they can cause serious problems for vehicles.
Potholes may seem innocuous, but they can cause serious problems for vehicles.
New high-tech solutions in Japan
Recent advances in digital technology are changing the way road repairs are carried out. Drones are used to quickly assess damaged areas, while remote-controlled machinery allows work in unstable terrain without risking human lives. IoT-based management systems monitor construction conditions in real time, improving accuracy and reducing delays. Digital modeling is used to create virtual replicas of road conditions, making it easier to plan repairs and anticipate difficulties. These modern tools enhance safety and speed up recovery.
The portability and utility of drones make them an indispensable tool for disaster recovery efforts.
The portability and utility of drones make them an indispensable tool for disaster recovery efforts.
IoT-based real-time data management can be used to create detailed, up-to-date maps that can help both the public and road workers gauge the status of recovery efforts.
IoT-based real-time data management can be used to create detailed, up-to-date maps that can help both the public and road workers gauge the status of recovery efforts.
Roads of the future
Japan’s history of roads and its recovery from natural disasters have fostered a culture of infrastructure innovation, keeping the country at the forefront of road technology. Beyond rapid repair methods and sustainable construction, there are constant new ideas being researched and developed. Constant innovation shows that Japan’s road engineering is not only about resilience in the face of natural disasters but also about preparing transportation networks for a low-carbon future.