Japan introduces guidelines for barriers at flood-prone underpasses
New guidance links advance traffic restrictions to weather alerts and rainfall levels, while drainage abnormalities also require measures to prevent vehicle entry.
- Japan's transport ministry has released new guidelines for installing remote-controlled barriers at high-risk, flood-prone underpasses to block vehicles during heavy rain.
- The barriers are to be activated based on specific triggers, including Level 4 emergency warnings, forecasted heavy rainfall, or failures in drainage systems.
- The new measures were prompted by recent fatalities in flooded underpasses, and the government will provide budgetary support for the installation projects.
- Local governments are now responsible for classifying underpasses into four levels of flood risk to determine where barriers are most needed.
Underpasses at particularly high risk of flooding should be equipped with remote-controlled barriers to keep vehicles out during heavy rain, under guidance Japan’s transport ministry released on Tuesday (October 6).
Weather alerts equivalent to a Level 4 emergency warning, or hourly rainfall reaching or being forecast to reach a specified level, should trigger advance traffic restrictions.
Restrictions and measures to prevent vehicle entry are also required if abnormalities are detected in drainage facilities.
The barrier recommendations place particular emphasis on underpasses where flooding has previously caused casualties or property damage.
Local governments and other road administrators are responsible for determining the category for each underpass within a nationwide classification system comprising four levels of flood risk.
Deaths during heavy rain in August in Chiba Prefecture, east of Tokyo, were among a series of fatalities in flooded underpasses that preceded the ministry’s move.
“We will promptly take effective measures to prevent accidents in flooded underpasses, in collaboration with relevant organisations,” transport minister Tatsunori Ibayashi told a press conference.
“We will provide comprehensive budgetary support depending on progress in the (barrier installation) project,” he said.
Ministry figures put the number of underpasses nationwide at 3,841 as of the end of March 2025.
[Copyright The Jiji Press, Ltd.]
