Sentence:  At this time of crisis in our Nation 's commuter <WSD>railroads</WSD> , a new threat to the continued operations of the New York Central has appeared in the form of the Chesapeake + Ohio Railroad 's proposal for control of the Baltimore + Ohio railroads . 
Meaning of the word marked with <WSD> tags:  line that is the commercial organization responsible for operating a system of transportation for trains that pull passengers or freight