The Central Japan Railway Company has developed a technology to remove the dirt from glass windows simply by spraying water during the day. Metal with a photocatalytic effect is made into sheets and attached to glass. When hit by ultraviolet rays, water does not form drops on the sheet surface but rather spreads and flows off. Technology using this phenomenon has been applied to window glass on Shinkansen bullet trains. If this technology spreads to passenger vehicles it will no longer be necessary to wash windshields using soap, reducing the burden on the environment.