Sentence:  A lack of <WSD>lookouts</WSD> was partially responsible for the deaths of two track workers at Margam East Junction in south Wales on July 3, according to an interim report published by the Rail Accident Investigation Branch on December 5. [...] "The absence of a <WSD>lookout</WSD> with no involvement in the work activity removed a vital safety barrier," says the report. 
Meaning of the word marked with <WSD> tags:  A person on watch for approaching enemy, police, danger, etc.