Because they are shorter than a single pace line with the same number of riders, the reaction time problems that occur during deceleration are not as great. A variant of the double paceline is the rotating paceline. The line most sheltered from the wind will move faster than the other line. When the lead rider in the faster line clears the lead rider in the slower line he will move over to become the lead rider in the slower line and slow to the slower pace. As the last rider in the slower line drops behind the last rider in the faster line, the slower line rider will move over to become the last rider in the faster line.
P ulling off the front of the fast line is tricky.
You must clear the fast line and slow immediately to the slow line speed in order to not leave a gap in the slow line. The most common error made by newcomers to rotating pace lines is to continue pedaling hard for a few revolutions after leaving the fast line. Since the slow line is going slower, this rockets the rider several bike lengths in front of the slow line, leaving a gap, depriving the slow line of your draft, and forcing the slow line to accelerate to catch you. I deally, the difference in speed between the fast line and the slow line should be 1 to 2 mph. Since we have a wide ability spread on our rides, this difference can grow to 3 to 4 mph as stronger riders pull harder in the fast line and weaker riders try to recover in the slow line.