Evaluation and installation guidelines for advance warning signal systems

Several intelligent transportation system (ITS)-based methods have been identified across North America to provide advance warning for end-of-green indication at high-speed signalised intersections. One of these is the installation of an advance warning signal (AWS) system. In the state of Utah, the Utah Department of Transportation installed AWS systems at three locations in the Salt Lake Valley to provide advance warning to drivers on the change in signal indication from green to yellow and, ultimately, to red. The current installations were determined to be successful based on speed variability and safety criteria, thus introducing the need to develop proposed guidelines for installation and to identify future system locations. The purposes of this study are to outline guidelines for ITS-based AWS installation and to present an evaluation procedure for comparison of candidate sites. The methodology and procedure summarised can be used by other governing agencies to fulfil similar needs in their respective jurisdictions.