超速传感器发现有一段距离Behind, in the (normal) direction of travel
" class="glossaryLink ">在后面的Visual indication passed to a train driver to advise the speed, direction or route of the train. There are almost as many types of signals as there are railways but they fall into the following main categories:1) handsignals - used mainly where there are no fixed signals or where the fixed signalling has failed. 2) semaphore signals - a fixed lineside signal where the stop indication is displayed as a horizontally positioned arm and proceed as a 45º or vertical arm. 3) colour light signal - a fixed lineside signal showing light indications to drivers. 4) cab signals - where the indications are displayed in the driver's cab.
" class="glossaryLink ">信号如果火车在接近危险信号时以过高的速度通过它，它就会启动。
