Offsetting elements at a equal distance using along a curved element can be quite challenging with copy parallel tool.

Background

For the most part using the move/copy parallel tools does just the tool implies, it will copy elements at designated value paralled to the orignal. The challenging part is when the element is not a straight line.

Steps to Accomplish

Go to the Home>Manipulate ribbon. Click on the construct array tool

1. Select the element to be arrayed

2. Identify the path element by selecting the endpoint of the element i.e. arc,b-spline curve, or curve

3. Turn on Rotate Items option, If on, the element(s) are rotated to maintain their relative orientation to the path element. 
   1. 

4. Move mouse along element path to define direction in which the array should be constructed. Number of copies will automatically increment as the cursor is moved along the path
5. Click left button on mouse to accept last point to begin the array

(Along Path array type) Sets the way that the array is created.

• Number — Defines the number of items in the array, via the Copies setting.
• Distance — Defines the distance between items in the array, via the Distance setting.
• Both — Defines the number of items in the array and the distance between each item, via the Copies and Distance settings respectively

See the following video for difference between move/copy parallel and construct array along path:

See Also