Abstract: The status of the traffic signals is repeatedly monitored. A visual display is presented of the spatial arrangement of the traffic signals in the system. The currently monitored status of the traffic signals is repeatedly represented on the display, spatially coordinated with the display of the respective traffic signals. A plurality of previously monitored statuses is also repeatedly represented on the display, spatially coordinated with the respective traffic signals and a traffic speed progression representation therebetween. The display distinguishes between through green and local green traffic signal status. A comparison is made of the currently monitored status of a traffic signal under consideration with the previously monitored status of the adjacent traffic signals as the latter arrives at the traffic signal under consideration and a separately distinguishable mark represents a discrepancy in the comparison when the previously monitored status is through green.