This expression is used to talk about changing means of transportation from N1 to N2.
から marks a starting point where the change begins, and に marks the final point or the goal.
父は しんじゅく駅で ちかてつから バスに のりかえます。
My father changes from a subway to a bus at Shinjuku Station.
母は ぎんざ駅で バスから 電車に のりかえます。
My mother changes from a bus to a train at Ginza Station.