The research team identified and executed a research plan consisting of 13 tasks that were needed to accomplish the project objectives.

Task 1. Form an Advisory Group of a minimum of five knowledgeable professionals to work with the project panel in the evaluation of PPLT signal displays. Members of the advisory group will be well-respected, experienced traffic engineers knowledgeable in the PPLT issue. The research team will also interact with the Signals Technical Committee of the National Committee on Uniform Traffic Control Devices (NCUTCD) on a regular basis. The objective of these frequent meetings will be to provide a regular flow of information to the committee.

Task 2. Develop an evaluation matrix and conduct an engineering assessment of the different displays. The evaluation matrix will include safety, operations, implementation, human factors, and versatility. The engineering assessment will identify factual and judgmental information required to evaluate the proposed displays. Included in Task 2 is the administration of an agency survey. The objective of the agency survey is to identify and quantify the different types of protected/permitted left-turn signal displays used in the United States.

Task 3. Conduct photographic driver survey to determine driver understanding of the six basic PPLT displays using static and dynamic survey techniques. At a minimum, computer generated displays on static background photographs will be used to represent the dynamic aspects. A minimum of 300 responses will be obtained in each of eight regions where the different displays are used (2,400 responses total). Geographic locations to be surveyed are Seattle, Portland, Reno, Dallas, College Station, Orlando, Dover, and Detroit. Select survey candidates to be representative of the driving population.

Task 4. Conduct traffic operation studies to determine and compare traffic conflict rates for protected/permitted left-turn signal displays. The traffic observation studies will be completed in the eight survey areas to provide additional insights in driver behavior related to alternative PPLT displays. Eight hours of conflict data will be collected at three intersections within each geographic area. The research team will work with local traffic engineers to identify representative sites with PPLT displays and gather crash, traffic, geometry, and other relevant data to document conditions at each site.

Task 5. Conduct a review of crash data to determine and compare left-turn crash rates associated with various PPLT displays. Crash data will be obtained from the same sites evaluated for the traffic observation studies (Task 4), and from selected components of the crash database created in 1988 as part of a previous study by JHK & Associates, if possible. Crash data will also be requested from volunteer network established early in the project.

Task 6. Conduct a comprehensive analysis of the results obtained from the agency surveys, photographic driver surveys, conflict studies, and crash studies.

Task 7. Prepare a draft version of the video driver survey. The objective of this task is to develop a working prototype of the animated survey for panel review. The video driver survey will be used to assess driver understanding of alternative protected/permitted left-turn displays.

Task 8. Prepare an interim report which documents the findings of Tasks 1 through 6. An interim report will be completed that will contain the findings and preliminary recommendations from Tasks 1 through 6.

Task 9. Prepare for and conduct first panel meeting. The objective of this task is to provide the opportunity for the panel and advisory group members to the discuss the project and results obtained to date with the research team. The research team will prepare a meeting agenda that will systematically review the evaluation findings, assess the importance of further studies, and narrow the list of viable PPLT displays for further testing. The panel will determine at this meeting which displays will be the focus of further testing and whether the original testing plan is still valid.

Task 10. Prepare a driver confirmation study and implementation study using full-scale dynamic driving simulators located at the University of Massachusetts (UMass) and the Texas Transportation Institute (TTI), the Research Team developed a virtual driving environment to further test driver understanding of select PPLT displays and associated behavior. Study participants were required to navigate a virtual world containing various signal displays, different arrangements and locations, and opposing traffic, with the intent of evaluating driver performance at pre-selected intersections controlled by PPLT displays in an actual driving environment. The researchers at UMass and TTI were tasked with each testing 200 drivers of various demographic backgrounds.

Field implementation of an experimental flashing yellow arrow display was conducted to field test a display that had shown promise in safety and driver comprehension in previous task activities and had ranked high in the Engineering Assessment. Volunteer agencies were sought from across the United States to install and operate the experimental flashing yellow arrow display.

Task 11. Prepare second interim report. The objective of this task is to document the results of all previous tasks. The second interim report will contain the findings and recommendations from Tasks 2 through 10.

Task 12. Prepare for and conduct second panel meeting. The objective of this task is to provide the opportunity for the panel and advisory members to discuss the results of the project with the research team. This final panel meeting should result in consensus on the recommended uniform display(s) for exclusive/permissive left-turn.

Task 13. Prepare final report. The research team will prepare a final report that will objectively document the research study methods, their associated findings, and the results of the panel meetings. The report will include appropriate statistical analysis to support the validity of the findings. The report will include a recommended standard(s) for the protected/permitted left-turn display, with supporting justification aimed at convincing practicing traffic engineers on the selection of the proposed standard(s). The final report will also include an implementation plan.