Minecraft wiki entry for Minecart_booster, associated text: Cart 1 is a simple uphill booster used to force cart 2 back to its initial position. Cart 2 actually drives the rider's cart (cart 3). Point 4 is a position for a switch that will allow cart 3 to exit the loop. The rider can then enter at any point after point 4. Point 5 shows the return track for Cart 3. The rider can exit at any time before point 5 or after point 4 safely (cart 3 will likely go around its full track again, so this design is inefficient for long tracks).