The Minnesota Department of Transportation (Mn/DOT) has concluded that at certain high speed locations, providing additional information to the motorist describing the operation of the traffic signal can assist the driver in making safer and more efficient driving decisions. The additional information includes a visual indication to get the driver's attention and a specific notice that the driver must prepare to stop. The Advance Warning Flasher (AWF) is a device which Mn/DOT uses to convey this information to the driver.
The Mn/DOT A WF system consists of a flasher and a sign located on main street approaches to a high speed signalized intersection. The AWF is connected to the traffic signal in such a way that when the main street green is about to change to yellow, the flasher is turned on to warn the approaching drivers of the impending change. Basically, the purpose of an optimally designed combination of traffic signal and AWF system is twofold: 1) to inform the driver in advance of a required driver decision (prepare to stop) and 2) to minimize the number of drivers that will be required to make that decision. Over time, questions have arisen regarding the use and application of AWF devices. The purpose of this study was to examine the effectiveness of the current AWF operation and, where possible, to make recommendations to improve it.
The study concluded that the use of AWF devices can be effective at reducing right angle and rear end accidents under certain situations but that the device does not automatically increase the safety of all intersections. Accordingly the device should be considered as a traffic engineering tool to be used to correct situations of special need. Further, this study developed a scheme to optimize AWF operation. The proposed approach will theoretically produce an optimized A WF location/operations scheme but must be field validated as part of a suitable test study.
