Easy way to create a new curve half way between two others?

I may have overlooked something basic, but is there an easy way of creating a new curve in between two other curves?
For example, a draw an arc and a straight line side by side. Is it possible to create a new line that finds the center distances and create a new line there?

I found it myself thanks. I was using the wrong search terms:
Curve > Tween Curves