Car shuttle or car shuffle?

Probably a strange question, but which is the right phrase - or the one people use most?
I always thought the term was "car shuttle" because you shuttle back and forth - like a shuttle bus. But there are quite a few reference in here to "car shuffles" to get to the start or end of a one-way walk.
Just curious ...
I always thought the term was "car shuttle" because you shuttle back and forth - like a shuttle bus. But there are quite a few reference in here to "car shuffles" to get to the start or end of a one-way walk.
Just curious ...