Event detection based on loop and journey time data

An algorithm that examines the travel time (TT) and the corresponding loop-based information at the same time is proposed. It monitors TT and the traffic speeds on all the loops within the TT section continuously. Event alerts are activated when there is a significant reduction of speeds on at least one loop detector in addition to a significant increase in the TT. An event may be detected by TT at some stage, by loop data at another stage, or by a logical combination of two. The algorithm using fixed thresholds has been tested based on operational data collected in the National Traffic Control Centre. The thresholds are determined based on tradeoffs between detection and false alarm rates (FAR). Test results based on a full day of data indicate that the integrated algorithm has achieved an impressive detection rate and a FAR which should be easily manageable by operators. Further work would be needed to confirm operations and facilitate a practical implementation.