In some cities, a thirdrail provides power to a subway train, usually operating underground; electricity passes through the rail.
在一些城市,第三道铁轨(电动机车的输电轨)给通常在地下运行的地铁列车供电,电力通过这道铁轨传输。
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That is a slightly lower proportion than in Greece or Sweden, but far higher than in America, where raising fuel taxes is nonetheless said to be a "thirdrail", deadly to politicians.