Citation

Bonneson JA, McCoy PT. Transp. Res. Rec. 1994; 1464: 42-50.

Copyright

(Copyright © 1994, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

Driver comprehension of protected and permitted left-turn (PPLT) signal designs was evaluated by conducting a survey of 1,610 drivers. The survey included a perspective view of an intersection approach and its traffic signal display, followed by multiple-choice questions about the correct driving action. The survey questions were focused on four display indications in six different PPLT designs. The display indications included (a) permitted left-turn, (b) protected left-turn only, (c) overlapped left-turn and through, and (d) a modified form of the protected left-turn only indication. The modified indication deviates from the "Manual on Uniform Traffic Control Devices" guidelines for PPLT heads (which require both a green arrow and red ball) by displaying only the green arrow during the protected indication. The six PPLT designs varied in terms of the location of the signal head with respect to the lane line, the arrangement of the lenses in the signal head, and the inclusion of an auxiliary sign. The survey results indicate that drivers are better able to understand PPLT designs with any of the following characteristics: a modified protected indication, the PPLT head centered over the opposing left-turn lane, and no auxiliary sign.

Language: en

Keywords

Design; Intersections; Traffic signals; Traffic signs; Surveys; Highway traffic control; Behavioral research; Control equipment