2-cm metal object causes short circuit on NS Line, leading to delays

Citation: http://www.straitstimes.com/breaking-news/singapore/story/2-cm-metal-object-causes-short-circuit-ns-line-leading-delays-20130403

In Japan, about a week ago, a hanger dropped out from a nest of birds caused blackout along whole Keihan Line.
What we can say to both of the accidents in Singapore and Japan is that "How can we prevent rail tracks from foreign objects?"

In order to reduce casualties falling on tracks, railway companies began to install platform screen doors. But, it won't be sufficient measure for tiny foreign objects.