1. A computer-implemented method for computing optimal public transportation transfer patterns between transit stations, the method executed by a computer system and comprising: for each stored public transit trip that describes a source station and a target station, retrieving a stored transit route that describes a schedule of one or more stops at transit stations by a transit vehicle during the public transit trip from the source station to the target station; generating a transit graph by representing each stored public transit trip's retrieved route as a sequence of a plurality of nodes connected by arcs, each node in the transit graph representing an event occurring at a transit station made by a transit vehicle associated with the transit trip; for each pair of transit stations represented in the transit graph: calculating from the transit graph at least one optimal transfer pattern that describes an optimal transit route of one or more transfers at transit stations between the pair of stations represented in the transit graph; and storing the at least one optimal transfer pattern for each pair of transit stations.