I found this by mistake and not entirely sure if it is faster then just driving around.
You can fall out of the map by charging your k-drive by holding down A button and press down on LS for full speed and run directly into the border straight on (don't hit it on an angle). When you fall off your k-drive and go out of bounds, quickly equip the k-drive again and drive forward a bit. You will start to free fall out of the map and you will be able to perform tricks which you could get 3,000 trick points for standing. When the falling stops it takes you back to Fortuna's gates. I found that the further the distance you were from Fortuna the more distance you traveled. I've been going to the North East of the map which I believe is the longest distance away and each time I get a white tick on the Achievement tracker.
Here's a video:
Sorry, this Game Clip has been removed