as the title, line length is directed related to a total number, representing the budget, which can be rewarded at the end of each week.
Meanwhile, the fare is collected upon every complete travel, those number will be reflected in the budget number, but the player can set the price tag. Lower price attract ridership, but the system budget may grow slow. Higher price may cash in fast, but dont scare away the commuters with overpriced tickets.
The reason for those system is to introduce a AI or Online player mode that compete on the same map. The fare setting is very critical, and may vary based on your lines capacity and strategy.