The March subway collision in Tokyo that killed five passengers and injured 63 others was caused by a combination of factors, including a wheel load imbalance and improperly ground rail surfaces, a Transport Ministry investigative panel concluded Thursday.
Upon receipt of the panel's final report, the ministry plans to order all railways to keep wheel load imbalances to less than 10 percent, check and correct track distortions, properly grind rails and maintain the proper angle of wheel flanges.
The report also urges railways to install additional rerailing frogs where necessary.