Sentence:  They slept where they could, sometimes in an empty truck on a <WSD>siding</WSD> near the station, sometimes in a cart behind a warehouse; [...] 
Meaning of the word marked with <WSD> tags:  A second, relatively short length of track just to the side of a railroad track, joined to the main track by switches at one or both ends, used either for loading or unloading freight, storing trains or other rail vehicles; or to allow two trains on a same track to meet (opposite directions) or pass (same direction) (the latter sense is probably an American definition).