Common carriers shall, according to their respective powers, afford all reasonable, proper, and equal facilities for the interchange of traffic between their respective lines, and for the receiving, forwarding, and switching of cars and property to and from their several lines, and to and from other lines and places connected therewith; and shall not discriminate in their accommodations, rates, and charges between such connecting lines. Any common carrier may be required to switch and transfer cars for another, for the purpose of being loaded or unloaded, upon such terms and conditions as may be ordered by the department.