Sentence:  Overhead construction was <WSD>catenary</WSD> rather than a single wire to allow the use of pantographs instead of trolley poles so that speeds could be higher. 
Meaning of the word marked with <WSD> tags:  A cable, the segments of which between supports take a catenary geometric shape, supporting in turn an overhead conductor that provides trains, trams or trolley buses with electricity, or the combination of the conductor, the cable, and supports. (Rail transportation)