Aging bridges of Japan

The collapse a month ago of a freeway bridge over the Mississippi River near downtown Minneapolis offers an important lesson for Japan, where a large number of bridges are expected to reach the end of their useful life in the near future. The collapse points to the danger inherent in old infrastructure for which repair needs have been ignored. The central and local governments must get serious about systematically reinforcing or replacing old bridges.

The 580-meter-long Interstate 35W bridge was built in 1967. The ferro-concrete structure, spanning the 120-meter-wide river, has four lanes in each direction. About 50 vehicles fell into the water when it collapsed; so far, 13 deaths have been confirmed. The bridge was used by up to 200,000 commuters every day.

Japan's transport ministry believes that a similar bridge collapse is unlikely in Japan because the government has switched to the policy of carrying out preventive repairs in time. But complacency must be avoided. Roads, bridges and tunnels are getting old in Japan as well. According to the ministry, the nation has about 140,000 bridges, each 15 meters long or longer, that are used by vehicles. In fiscal 2006, 6 percent of those bridges were 50 years or older. That age category will rise to 20 percent in fiscal 2016 and 47 percent in 2026. It is usually assumed that a 50-year-old bridge should be replaced.

Since an enormous amount of money will be needed to replace all old bridges, the central and local governments are trying to prolong the life of old bridges by detecting weaknesses and carrying out repairs in advance. But as of February 2007, only 13 percent of the nation's municipalities were conducting regular checks of bridges.

An encouraging sign is the formation of an association comprising Kyoto University, the ministry's Kinki Regional Planning Bureau, construction companies and other organizations to study ways to improve bridge inspections with the use of high technology. The central and prefectural governments need to extend technical support to municipalities. Better ways to financially support them also should be considered.