Modeling driver visual demand on three-dimensional highway alignments

This research focuses on evaluating driver visual demand on three-dimensional (3D) highway alignments, consisting of combined horizontal and vertical alignments. Using a driving simulator, nine two-dimensional and 3D hypothetical alignments for two-lane rural highways were developed following the standard guidelines of the Transportation Association of Canada. Fifteen driver subjects drove in the simulator and data on visual demand were analyzed using different processing and statistical software. The results showed that visual demand on 3D curves significantly varied with the inverse of the horizontal curve radius and the inverse of the vertical curvature. Meanwhile, the subject age had a significant effect on visual demand. Models for evaluating visual demand oil 3D highway alignments were developed for both curves and tangents. The developed models were verified and applied to 3D alignments to carry out a design consistency evaluation.