ahead vs straight ahead

ahead

adv
  • At an earlier time; beforehand; in advance. 

  • To a later time. 

  • To an earlier time. 

  • In or for the future. 

  • At or towards the front; in the direction one is facing or moving. 

  • So as to be further advanced, either spatially or in an abstract sense. 

straight ahead

adv
  • directly ahead, without deviation 

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