Motorist interpretation of potential transition symbols in a freeway lane control signal array

Abstract

This thesis documents licensed driver response to, interpretation of, and perceived urgency of response to freeway lane control signals (more s . pacifically to the yellow X and yellow diagonal arrow) when displayed in a scene depicting a three-lane freeway section containing a lane control signal array. Each of the arrays tested consisted of some combination of freeway lane control signal symbols which included one of the candidate yellow symbols, at least one green down arrow, and either one or no red X. The response offered most frequently by survey subjects when asked what they would do if travelling in the lane below any of the candidate yellow symbols was "move to the lane with the green arrow". However, it was observed that subject responses to the yellow diagonal arrow varied less than those to the yellow X when the red X was introduced into the lane control signal array. Regarding subject interpretation of the candidate yellow symbols, the meaning offered most frequently by survey subjects was "lane closed, blocked, or closing". The second most frequent interpretation of both candidate yellow symbols when shown with green down arrows only was "lane ends physically"; however, introduction of the red X into the lane control signal array altered subject perception, and "lane is congested" became the second most popular meaning. Although the average median distance to the lane change maneuver was identical for both the yellow X and yellow diagonal arrow, subjects' perceived urgency of response to both candidate yellow symbols were similar regarding subjects' introduction of the red X into the lane control signal array. However, this affect was more pronounced for subjects viewing the lane control signal array containing the yellow X. While results for the two candidate yellow symbols were similar regarding subjects' interpretation and perceived urgency of response, analysis of their indicated reaction revealed an interesting difference. Subjects viewing the lane control signal arrays containing the yellow X were more likely to indicate a reaction considered "incorrect" given the intended use of the candidate yellow symbols than they were when viewing the arrays with the yellow diagonal arrow.