Red has meant stop since long before cars existed, with train signals' use of red dating back to the days when mechanical arms lifted and lowered to indicate whether the rail ahead was clear.

红色很早以前就被用作火车信号，那时汽车还没出现，而铁路用机械臂板上升下降来代表前方是否有火车驶来。

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If, as some researchers suggest, romantic love can be broken down into electrical impulses in the brain, then why not train the mind to simulate those signals while looking at an inanimate character?

如果和某些研究人员所说的那样，浪漫爱情的刺激可以分解为大脑中的电子脉冲，那么何不训练头脑在观看无生命的人物时模拟出刺激信号呢？

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Also left unexplained was why railway signals did not stop the second train before it hit the first one.

另外，在第二辆列车冲向第一辆列车前，为何没有铁路信号加以阻止。 这也同样令人匪夷所思。

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Nine safety board teams will examine aspects such as train operations and communications, signals, tracks, crash-worthiness of equipment, maintenance and survivability -- ease of fleeing the trains after the crash and other survivability factors, Hersman said.

CNN: Investigator: D.C. Metro crash 'a scene of real devastation'

On the eve of Thanksgiving, several days before the World Trade Center line reopened, Mr. Lejda and a colleague walked through the river tube, he said, hanging up speed limit signs in the tunnels, since the train operators would be without the lighted signals that usually signal when and where to slow down.

WSJ: PATH's Road Back Is Rocky

She is attempting to train several tame elephants to respond to such signals by shutting them inside a gently vibrating truck.

ECONOMIST: Extra sensory perception