Any railroad company may appoint one (1) or more persons to be designated by such railroad company as a railroad policeman to aid and supplement the law enforcement agencies of this state in the protection of railroad property and the protection of the persons and property of railroad passengers and employees: Provided, That the appointment of any such person as a railroad policeman shall be subject to the approval of the attorney general of this state or any person that he might designate for such purpose. While engaged in the conduct of his employment, each railroad policeman so appointed shall possess and exercise all law enforcement powers in every city and county of this state which are prescribed by law for the sheriffs of the several counties and for the police officers and city marshals of any city. Each railroad policeman shall carry upon his person at all times while engaged in the conduct of his duties an identification card setting forth the date of his appointment and signed by the attorney general or his designated agent.