Round Up your Wagon (wheels):
Let make us some wagon tracks ignoring the whole horse wear in the center in favor or the expected wheel ruts, because this is a map and we get to make things representative rather than illustrative sometimes.

First off we need a wagon wheel brush. Lets open a new file and create a new layer. On it we are going to put two dots:
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Very complex I know.
-Select it all (ctrl+a)
-edit => define brush preset
-Go into your brush tab and turn the spacing way down
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-Go into shape dynamics in that brush tab and change the angle control to "direction"
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Save the brush!

Now create a new layer on your map.
using the pen tool draw out your wagons path
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go back to you brush tool make sure your wagon rut brush is selected and black is your foreground color and hit enter (this will stroke the path you made with the pen tool with your brush)
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Yay its ugly!
First lower the fill of the layer to something small (say 14%) you can adjust the over all opacity later if you like also.
Lets add some emboss to it, you can see the settings I used and imitate them or mess around till you get something you like better:
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next to make it look a little more imperfect we will add some of the "texure" option to our emboss choosing any old dirt looking pattern we have laying around:
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Finally well put that whole layer in a folder (control+G) and put a layer mask on the folder. We then just need to use a blurry edged brush set to low opacity and randomly lighten up some of the path to break up the evenness. there we go one wagon wheel rut.
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