Social media has become an integral part of modern communication. There is however no clear consensus among transportation managers on how social media could or should be used to collect or disseminate actionable information. To provide guidance on the potential use of social media in transportation, a better understanding is needed of the message content as well as the path taken from the sender to the potential user of actionable information during crises and other non-routine events in the transportation system. This report assesses how social media is used to support traffic management operations during planned special events such as concerts and sporting events, and unplanned disruptive events, such as accidents and weather events.