Introduction[]
Fastpass is an Infinite mode achievement in Run 3. This achievement is found in IM level 213.
Gameplay[]
The Conveyor tiles are right at the edge of the platform, so you need good maneuverability and careful jumps to stay on them. The best characters would, therefore, be the Runner and the Student, who have good maneuverability and can do consecutive jumps.
Or you could just fly through the air with the Gentleman, and it will still work even if you touch nothing. Just make sure that if there are no power cells in range, to land on a conveyor tile.