Ok so what you want to do is start patrol (anywhere will do).
From there, push start and select "road map". If you move the map around to the edge, you will see an orange circle with two arrows in it (they are usually North, South, East, West). Now drive to one and stop in it when you get there. The screen will then load, and you will go from town to country or vice versa.
Now drive forward a bit and the orange circle will re-appear so you can just drive back into it. Repeat this 10 times in total and achievement will unlock
Should take 5-10 mins tops. Good luck!!