Development of a uniform traffic signal display for protected/permitted left-turn control /
A comprehensive assessment of protected/permitted left-turn (PPLT) signal displays was performed considering current usage, safety, operational performance, and driver understanding measures. Information from 168 transportation agencies, at least one in each of the 50 states, was used to quantify th...
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| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1999.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=733668261&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | A comprehensive assessment of protected/permitted left-turn (PPLT) signal displays was performed considering current usage, safety, operational performance, and driver understanding measures. Information from 168 transportation agencies, at least one in each of the 50 states, was used to quantify the attributes of more than 107,000 signalized intersections. Traffic safety and operations were evaluated by field studies at 24 intersections containing PPLT signal phasing, three each in eight geographical study locations. Driver understanding was evaluated through a computer based photographic driver survey completed by 2,465 drivers. In total, 73,950 survey responses were received pertaining to the 35 different survey scenarios evaluated. Approximately 29 percent of all intersections in the United States contain PPLT signal phasing. Ninety-eight percent of these intersections use a green ball indication for the permitted phase. The remaining two percent use either a flashing yellow arrow, flashing yellow ball, flashing red arrow, or flashing red ball indication. No evidence was obtained to suggest that the type of PPLT signal display affected conflict rates, saturation flow rate, or start-up lost time. A significant number of traffic events were found during the protected left-turn phase when the five-section horizontal display simultaneously presented the green arrow and red ball indications. Variation in response time between study locations was related to differences in the signal phasing sequence. The photographic driver survey results suggested that drivers have a good understanding of the prohibited (all-red) and protected only left-turn indications. The flashing red ball permitted indication had a significantly higher correct response rate than the green ball permitted indication although less than 64 percent of drivers correctly responded. Drivers over the age of 65 found the flashing ball permitted indications easier to comprehend, and responded more quickly with less fail critical errors than with the steady green ball permitted indication. The flashing red ball permitted indication in a three-section vertical display outperformed all other indication and display combinations, including the most commonly used five-section cluster display with a green ball permitted indication; however, additional study of the flashing permitted indications is required. |
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| Item Description: | Vita. "Major Subject: Civil Engineering". |
| Physical Description: | xx, 328 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 279-289). |