Fineliner is an experiment to simplify and structure the raw transit lines operators publish into a simplified representation of a transit network.
Transit operators often publish their transit lines as accurately as possible, with the exact coordinates of each track section the train will travel over. While this is useful data, most users would rather see something that looks closer to a transit map.
Fineliner takes the raw transit lines and simplifies them into a more abstract representation, where the shared segments of each lines are grouped, much like how a transit map would show them. This makes it easier to scan at a glance.