Refers specifically to police officers responsible for railway security and public safety on trains and at stations.
Railway police are patrolling the station.
鉄道警察 is the railway police force as an organization; 公安官 is an individual officer within it.
railroad security officer
Compound of 公安 (public safety) and 官 (official). The exact historical derivation is uncertain; the term is conventionally associated with railway police duties.