- Tomoki Moriyama
Why「電車をおります」 instead of 「電車におります」is correct?

「を」might be one of first particle that you learned in basic level. But the particle has one more function - it indicates direction: 'go out' or 'be away'. Remember this function of this particle and you will easliy remember why some verbs require 「を」to show place/transport.
電車を降(お)ります。
get off train.
家を出(で)ます。
leave house.
Ngee Ann Polytechnic を卒業(そつぎょう)しました。
graduated from Ngee Ann Polytechnic.
授業を休みます。 be absent from lesson.