signpost vs warning sign

signpost

noun
  • A post bearing a sign that gives information on directions. 

  • A word or phrase within a clue that serves as an indicator, rather than being fodder. 

verb
  • To indicate logical progress of a discourse using words or phrases such as now, right, to recap, to sum up, as I was saying, etc. 

  • To install signposts on. 

  • To signal, as if with a signpost 

  • To direct (somebody) to services, resources, etc. 

warning sign

noun
  • A sign that indicates a danger, for example to vehicles on a road or of hazardous chemicals. 

  • An indication that someone or something is in danger or at risk 

How often have the words signpost and warning sign occurred in a corpus of books? (source: Google Ngram Viewer )