ambulance vs mode of transport

ambulance

noun
  • An emergency vehicle designed for transporting seriously ill or injured people to a hospital. 

  • A mobile field hospital. 

verb
  • To transport by ambulance. 

mode of transport

noun
  • Any form of vehicle or system used to transport people or goods. 

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