Do dotted extensions help guide drivers at a transition area of partial-shadowed left-turn lane? An investigation based on eye movement behavior and visual attention

When adding an exclusive left-turn lane at an intersection, a transition area is needed to allow through and left-turn traffic to move into appropriate lanes smoothly. However, whether a dotted extension should be applied at such a transition area remains inconclusive. The need for recommending a dotted extension is further complicated at intersections where an approach taper partially shadows a left-turn lane. This study aims to shed light on whether dotted extensions should be recommended in a transition area and research the impacts of dotted extensions on guiding drivers from their perspectives. Scenarios with and without dotted extensions were created for a video-viewing experiment. Driver eye movement behavior and cognitive load rating served as evaluation indicators in each target scenario. Thirty participants were recruited and randomly assigned to with and without dotted extension groups. Results show that: (1) With the dotted extension, participants could focus on fewer objects and, therefore, would not need to divert their visual attention toward the surrounding vehicles. (2) The dotted extension assists through-traffic drivers in maintaining more focused attention on information critical to their driving task. (3) Dotted extensions help drivers reduce stress, mainly because of clearer indications of lane configuration. Altogether, our findings suggest that a road with dotted extensions provides better guidance in a transition area than one without dotted extensions.