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Photographic Driver Survey 

Data collection for the Photographic Driver Survey was completed in Troy, Michigan; Dover, Delaware; Portland, Oregon; Dallas and College Station, Texas; Orlando, Florida; Cupertino, California, and Seattle, Washington.

Additional surveys were administered by volunteers in Eugene, OR; Boca Raton, FL; Jackson, MS; Raleigh, NC; and Corpus Christi, TX.

The objective of the photographic driver survey was to evaluate the different PPLT signal displays used in the United States. The evaluation explored driver understanding of the signal indications under a variety of conditions. The conditions varied through the use of protected left-turn indications, permitted left-turn indications, through movement indications and PPLT signal display arrangements.

More than 2,465 drivers took the survey. At each of the project team's survey locations, approximately 300 drivers completed the survey. Because each survey respondent was presented with 30 scenarios, a total of 73,950 responses were recorded.

The findings and conclusions of the photographic driver survey are documented in Working Paper 3.  

Traffic Operations

The Research Team collected and analyzed left-turn saturation flow rate, start-up lost time, response time, and follow-up headway data at the eight geographic locations where the driver survey was administered (Dallas, Dover, Delaware, Oakland County, College Station, Seattle, Portland, and Orlando). The results of the traffic operations studies are documented in Working Paper 4.

Traffic Conflict Study

The Research Team collected conflict data at 24 study intersections to quantify the left-turn conflict rate and event rates for different PPLT signal displays and indications. Traffic conflicts are traffic events involving the interaction of two or more drivers where one or both drivers take evasive action to avoid a collision. Traffic events are unusual, dangerous, or illegal non-conflict maneuvers such as red indication violations, backing up, hesitation on signal change, and slowing considerably in a traffic lane. The results of the Conflict Study are documented in Working Paper 5.

Crash Data Analysis

The Research Team conducted a limited evaluation of crash history associated with the unique displays used in PPLT. The research panel members and research team recognized that current crash reporting techniques do not adequately document causes of a crash as they relate to traffic signal operation, much less the particular signal display. The objective of the crash analysis was to determine and compare left-turn crash rates associates with various PPLT signal displays. The crash analysis are documented in Working Paper 6.

Interim Report

The Research Team distributed an Interim Report that documented all of the work conducted up to August 1999. The interim report documented and summarized all of the work previously distributed in the working papers (1 through 6). The interim report provided recommendations on how to proceed in the project.

First Panel Meeting

The Research Team met with the Project Panel members on October 26, 1999 in Washington, DC.

Second Panel Meeting

The Research Team met with the Project Panel members on January 8, 2003 in Washington, DC.


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