Effect of turn signal usage on delay at three-legged intersections

The purpose of this study was to test the hypothesis that turn signal usage reduces stopped delay. Specifically, to test the hypothesis that turn signal usage by a right turning vehicle on the through roadway of a three-legged intersection reduces stopped delay to a waiting vehicle on the intercepted roadway. A total of seven intersections, four in the Saint Louis, Missouri, area, and three in the Knoxville, Tennessee, area, were studied. The data were evaluated using three different statistical analyses. A scatterplot of the average stopped delay per vehicle versus the percentage of turn signal usage by right turning vehicles was inconclusive. Both the binomial test and the Wilcoxin Rank Sum Test indicate that the hypothesis cannot be rejected for the 95% level of confidence.