Sidetracked

To divert (a locomotive or train) on to a lesser used track in order to allow other trains to pass.

To divert or distract (someone) from a main issue or course of action with an alternate or less relevant topic or activity; or, to use deliberate trickery or sly wordplay when talking to (a person) in order to avoid discussion of a subject.

"I hope you can sidetrack the teacher with questions so we don't have to take the exam."

To sideline; to push aside; to divert or distract from, reducing (something) to a secondary or subordinate position.

"He has sidetracked this debate for far too long."

To deviate briefly from the topic at hand.

"Just to sidetrack a little bit from the subject I will explain my reasoning."