How To Make Ruts?

[Parrillyzer]

Hey guys!

I have been spending some free time making a replica of the track I grew up riding. I am to the point where the track layout is defined but every corner is flat. I was thinking of adding some pre-made ruts to them but I am running into a wall on how to best accomplish this. I tried sculpting them in L3DT but they ended up super jagged and I wasn't happy with the end result. Is there an easy way to add it to the black/white heightfield in GIMP? Or maybe a method that is being used in Blender?

Help me finish up my track so I can publish for everyone to enjoy! 

Thanks in advance!!!