  Large urban special events significantly contribute to a city's vibrancy and
economic growth but concurrently impose challenges on transportation systems
due to alterations in mobility patterns. This study aims to shed light on
mobility patterns by utilizing a unique, comprehensive dataset collected from
the Helsinki public transport mobile application and Bluetooth beacons. Earlier
methods, relying on mobile phone records or focusing on single traffic modes,
do not fully grasp the intricacies of travel behavior during such events. We
focus on the Vappu festivities (May 1st) in the Helsinki Metropolitan Area, a
national holiday characterized by mass gatherings and outdoor activities. We
examine and compare multi-modal mobility patterns during the event with those
during typical non-working days in May 2022. Through this case study, we find
that people tend to favor public transport over private cars and are prepared
to walk longer distances to participate in the event. The study underscores the
value of using comprehensive multi-modal data to better understand and manage
transportation during large-scale events.
