A survey of licensed drivers was conducted at the 1988 indiana state fair to determine motorists' understanding of and preferences for left-turn signal alternatives including permissive, protected, and both protected and permissive (p/p) signals, and leading and lagging phase sequences. Survey responses were received from a diverse but generally representative sample of over 400 people. Statistics such as the respondent error rate during the understanding portion of the survey consistently indicated that the survey data were not biased in any substantive way. Several notable results emerged from the analysis of the survey responses. The protected signal was by far the best understood, whereas the p/p was the most often misunderstood. The left turn yield on green sign proved more confusing than the other p/p sign conditions tested, including the no sign condition. Among signals, the protected was most often preferred, and the permissive proved the least popular. For many reasons, the leading sequence was preferred by more respondents than the lagging sequence. This paper appears in Transportation Research Record No. 1281, Human Factors and Safety Research Related to Highway Design and Operation 1990.
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