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In the fiscal year 2022, investments in public roads for construction and maintenance amounted to approximately **** trillion Japanese yen, up from **** trillion yen in the previous fiscal year. Construction expenditures exceeded maintenance expenses in that year. According to the Ministry of Land, Infrastructure, Transport and Tourism (MLIT), the Ministry’s yearly expenditures on public infrastructure will increase by roughly 40 percent until around fiscal 2044 compared to 2018 to counter infrastructure deterioration.Ìý

What causes infrastructure deterioration?

The most relevant factors causing distress for materials used in road construction, e.g., asphalt, concrete, steel, are the building quality, temperature and humidity, load, as well as accidents and other damages. Each of those stress factors is relevant for Japan.
Inspections have shown that rapidly built structures are prone to damage in particular. Furthermore, as Japan has pronounced seasonal weather, the fluctuation of temperature and humidity may have a stronger effect. Moreover, water and other chemical substances in the environment trigger corrosion of steel, often affecting the soundness of bridges, for example. Even if structures are well-built and structurally sound, the load takes its toll on the integrity over time. The term fatigue refers to structural damage caused by a cyclical load that is well below static strength. In other words, even if roads are designed for a certain number of vehicles of a certain weight, they will eventually wear out. For this reason, Japan declared some roads as essential logistical roads (which include all arterial roads), where trailers are allowed to transport ** ft international marine shipping containers (up to ** tons) without a permit for special vehicles otherwise required.
Finally, accidents and other damages may impair the functionality of the infrastructure. These hazards are noteworthy for a country like Japan, where earthquakes, tsunamis, and landslides happen from time to time. Although proactive design can mitigate natural disasters, their hardly predictable forces usually have an impact to some degree. Naturally, the age of the structure exacerbates these stress factors.

Japan: The country of rapidly aging infrastructure

Maintaining an integral part of Japan’s road infrastructure will become a challenge. The Japanese road infrastructure has experienced a fast expansion since the 1950s, paralleling the economy’s rapid-growth period (and partly fueling it). By March 2033, 63 percent of road bridges and 42 percent of tunnels are expected to be 50 years old or more. Cyclical road maintenance inspections hint at the possible extent of infrastructure deterioration if no countermeasures are taken.
To judge the maintenance level of public roads, the government moreover calculates a maintenance rate. It takes not only into consideration the structural qualities required by legal standards but also the actual degree of congestion. The public sector aims to mitigate congestion, since it costs time and fatigues the road (and the people). The road sections with the highest congestion in Japan are typically those on urban expressways of Tokyo and Osaka.
Against the backdrop of infrastructure deterioration, the Japanese population is aging rapidly and shrinking. While the economy and life expectancy have continued to grow since the 1950s, birth rates have sharply fallen since then, resulting in the current-day demographic. This demographic structure will impact rural depopulating areas in particular, where there is a shortage of civil engineers already today.