The Number of Laps feature was added on April 11th, 2012. Within the update that allows you to publish your car into the multiplayer game, there has been another option added to the game: changing the amount of laps on a track. Basically, you can now change the number of laps to your liking. The highest number of laps any track can have is 15. So you can make it 1 lap on Twisted Revenge or 15 laps on 4D-Vertigo.