Available with 3D Analyst license.
Copy Parallel makes a copy of selected lines at a distance you specify. You can choose to copy the new lines to the left, right, or both sides of the selected lines. You can use the Copy Parallel command, for example, to create a street centerline or a gas line that runs parallel to a road. If you use Copy Parallel to copy lines on both sides of the selected line, you can create road edge of pavement lines from a street centerline. When using Copy Parallel, you need to choose a feature template, which specifies the layer that will store the new feature and the default attribute values that will be applied to the feature.
When copying, you can also specify the method for how corners are created. The graphics below show the different corner options, where the blue selected line is the original line that is being copied. The beveled option (left) adds a line segment to create a beveled corner. The mitered option (center) extends line segments until they intersect. The rounded option (right) adds a curved segment at the corner.
Copy Parallel works with one or more selected lines. Various options are available on the Copy Parallel dialog box to ensure that the lines are copied to the side you want.
If you select multiple lines and they form a single continuous line (regardless of the direction of the lines), the Treat selection as a single line option is enabled.
In the sketch below are two line features (shown as the blue selected line) whose endpoints are coincident. If you want to copy those lines to the left side, for example, you will get different results depending on which options you choose at the bottom of the Copy Parallel dialog box. If you uncheck the Treat selection as a single line option, a feature is created for each line in the selection, but each appears on the left side of the original features' directions.
If you check the Treat selection as a single line option, now when you want to copy to the left, you get one feature on the left, and the resulting selection of lines are all on the same side.
If you also check the Create new feature for each selected line option, a feature is created for each line in the selection.
If the Copy Parallel offset distance is large enough, self-intersecting loops may occur. Maintaining these loops allows you to retain any attribute values of the features. However, if you do not want them to be created, make sure you check the option for Remove self-intersecting loops. This option must be on when you check both the Treat selection as a single line and Create a new feature for each selected line.
For example, you are using Copy Parallel to create internal lines along a cul-de-sac street. In the graphics below, the blue line is the original selected feature to be copied (shown by itself on the left), and the black lines are the result of applying Copy Parallel with an offset large enough that self-intersecting loops are created. The center graphic shows the result when loops are created, while the right shows the result when the option is checked and loops are removed.