Advance warning signals (AWS) provide information warning drivers in advance of the end-of-green phase for an approaching signalized intersection. The purpose of this research was to develop guidelines for the placement of AWS in Utah, both conditions to evaluate the need for AWS installation and guidelines for the AWS system design. The conditions were based on literature of other transportation agencies that had similar AWS systems and were developed using the Policy Delphi method. The Policy Delphi method is the development of a specific policy area through the means of discussion by a committee of experts correlating views and information involving opportunity to react and assess different viewpoints until the committee is in agreement over the policies being recommended. Six conditions are recommended and discussed in detail, including: limited sight distance, posted speed, isolated intersection, high crash rate, approach grade, and heavy vehicle traffic volume. The guidelines for the AWS system design included details about three components: AWS component, advance detection component, and signal timing component. An evaluation matrix was developed by the Policy Delphi method for the purpose of evaluating and prioritizing a group of intersections for AWS installation. A total of 24 intersections were identified by the Utah Department of Transportation for this project that helped to develop and verify the conditions and evaluation matrix. The recommended guidelines and evaluation matrix results are described.

Advance warning signals installed upstream of a high-speed signalized intersection (HSSI) warn motorists of impending signal changes in an effort to reduce the frequency of red-light running (RLR) and crashes. A new advance warning signal design was tested on an approach to an HSSI in Utah to study the effects of the modified design on motorist behavior. The new design utilized an overhead dynamic blank-out sign and flashers. A state-of-the-art digital wave radar evaluation system was installed at the study site to collect continuous data of vehicle speeds and RLR events by a non-intrusive method. Crash data were collected from the jurisdiction responsible for the study site and for an additional control intersection. Data were collected prior to, immediately after, and eight months after installation The blank-out overhead dynamic advance warning signal (BODAWS) system reduced RLR at the site during the time period immediately after installation. Eight months later, the number of RLR violations was slightly higher on one approach than before BODAWS system installation. Crash results showed that six months after BODAWS installation, the number of crashes declined at the study site. The number of crashes proportionately declined at the control intersection as well indicating a need to continue to evaluate and monitor changes. Mean vehicle speeds recorded before the onset of the yellow signal increased on the approaches to the study site immediately after BODAWS installation, and remained higher eight months later. Mean vehicle speeds recorded during the yellow signal, increased eight months after BODAWS installation to speeds higher than before the system was installed. Higher speeds during the yellow signal, combined with an increase in the number of RLR violations eight months after BODAWS installation, suggest that motorists may have begun to use the advance warning to speed up in an attempt to enter the intersection before the signal turned red. It is recommended that the lead flash time between activation of the BODAWS signs and flashers and the onset of the yellow signal should be adjusted so that motorists are not provided with more time than is necessary to safely clear the intersection.