  Although severe mobility restrictions are recognized as the key enabler to
contain COVID-19, there has been few scientific studies to validate such
approach, especially in urban context. This study analyzes mobility pattern
changes in Seoul, South Korea that adopted adaptive approach toward mobility.
Intervention analyses reveal that major mobility reduction did occur two weeks
before the city's case peak. Such voluntary adjustments exhibit strong
preference shift toward private mode from public transit. Large reductions
occurred in non-essential and high-contact activities of shopping and dining,
while work and Starbucks trips were less affected. The collective evaluation
reveal that major changes in epidemiology, mobility and policy occurred
simultaneously, with no lagging nor leading contributors. Our study
demonstrates that collective understanding the mutual aspects among mobility,
epidemiology and policy is essential. Incremental and flexible mobility
restriction is not only possible but necessary, especially for a pandemic of
extensive spatial and temporal scales.
