I'm drawing maps in Illustrator. Our way of depicting divided highways is parallel lines with a fill. Here is an example:

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The way I did this was a 1 point yellow stroke, command c, command f, send to back, explained stroke to 2 points and make black.

These are a pain to make and edit. I'm wondering if there's a way to do this with a single stroke.


Yes! - Appearance panel to the rescue. You can duplicate the existing stroke by dragging it to the 'new' or paper icon. Then just make the second stroke larger. See my example for you below.

Appearance panel 2 strokes


I'd create pattern brush with any type of colors you want.

For example, I created 3 rectangles and dropped them to brush panel choosing in popping up panel Pattern Brush.

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After that you can apply this pattern to any path you want whenever you want without adjusting weights, borders etc:

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I also recommend making a brush. It can be useful to make a pattern brush from lines, because the result can be expanded to strokes.

I put three colors instead of two to show how it behaves:

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  1. Draw a horizontal (=hold shift) line, make 2 copies and give the needed colors and widths. You can select the colors as well in step 2.

  2. Align the lines. Most accurate result is got by aligning them at first to the same place and moving two of them up and down with Object > Transform > Move. My lines were 4pt wide, so I moved vertically +4pt and -4pt. Color selections can well be made after aligning the lines.

Select all and drag them to the brushes collection. Define them to be a pattern brush which is stretched to the needed length.

  1. A test curve is drawn with the pen

  2. The new brush is applied, NOTE:The curve is still a fully editable single path.

  3. Maybe useful to know that this is possible: The shape is expanded (Object > Expand Appearance). Then it's ungrouped three times. That splits the shape to separate bended lines. Two of them has been dragged aside and one is selected.

NOTE: If the original lines are longer than the curve, expanding appearance generates full length curve per color.

  1. Also maybe useful: Impossibly tight curves cause unexpected results:

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