Traffic Monitoring immediately after a major natural disaster as revealed by probe data – A case in Ishinomaki after the Great East Japan Earthquake

• Probe data reveals traffic condition immediately after earthquake and tsunami.
• It indicates a sudden transition of the vehicle speed lower than walking speed.
• The estimated traffic condition reveals the serious gridlock in Ishinomaki.

This study analyzes how people behaved and traffic congestion expanded immediately after the Great East Japan Earthquake on March 11, 2011 using information such as probe vehicle and smartphone GPS data. One of the cities most seriously damaged during the earthquake was Ishinomaki. Understanding human evacuation behavior and observing road network conditions are key for the creation of effective evacuation support plans and operations. In many cases, however, a major natural disaster destroys most infrastructure sensors and detailed dynamic information on people’s movements cannot be recorded. Following the Great East Japan Earthquake, vehicle detectors did not work due to the severe tsunami and electric power failure. Therefore, information was only available from individuals’ probe vehicles and smartphone GPS data. These probe data, along with disaster measurements such as water immersion levels, revealed the sudden transition of vehicle speed (i.e., it eventually slowed to less than walking speed and a serious gridlock phenomenon in the Ishinomaki central area occurred). These quantitative findings, which could not be identified without probe data, should be utilized during future disaster mitigation planning.