Incident Data Sample Clauses

Incident Data. Freeway incident data are available from three sources in Washington State: the WSDOT IR teams, the Washington State Patrol (WSP), and the WSDOT Transportation Systems Management Center (TSMC). Data collected by the WSDOT IR teams are stored in the Washington Incident Tracking System (WITS). This data set contains only information pertaining to the incidents for which WSDOT IR teams were present. Washington State Patrol data are stored in its Computer Aided Dispatch (CAD) database. This database contains information on all incidents reported to and handled by the WSP. The TSMC maintains its own incident log file with incidents observed by traffic surveillance video cameras. When the researchers determined which set of incident data would best serve the purposes of this study, three pieces of information were considered critical: incident start time, end time, and location. While both the CAD database and the WITS database contain these data items, the WITS database is preferable because of its higher data quality. Although the CAD data set has more data items than the WITS data set, it frequently misses critical pieces of information such as the beginning and clear times. Furthermore, the CAD data set is more difficult to obtain, as it includes drivers’ private data. Incidents recorded in the 2009 WITS database were therefore used in this study. State Route ID, direction, and mile post jointly define an incident’s location. Notification time records the time when an incident was reported to the IR program. Since most incidents were reported through mobile phones nowadays, notification time should be very close to the start time of an incident in metropolitan areas. Arrival time stores the time when an IR truck arrived at the incident location. All lanes open time is the time when all lanes became open to traffic. Clear time is the time when the incident had been fully cleared and the IR teams left the incident scene. In this study, an incident’s duration was defined as the time when traffic is under the impact of the incident. In the 2009 WITS data, this is labeled as Clearance Time. This can also be easily checked by periodically calculating IID with the proposed approach. When IID stops growing, impacts from the incident have ended.