Relationship between Speed Distribution and Horizontal Alignment on Rural Four-Lane Highways

This study defines the roadway geometry, as a part of the review process for inducing alignment design reflecting the desires of drivers traveling on the roadway. From the standpoint of roadway design technician or road user, the most important thing is to review design consistency to know how well roadway alignment under specific design speed can meet service in terms of roadway function or if safe driving at a roadway point is possible. Current design review approach assumes that traffic safety is secured only by specifying minimum criteria of road design. However, this approach oversimplifies the desires of drivers so that it would be considered as a passive method due to meeting only minimum design criteria. From the results of this study, it is possible to confirm that design inconsistency would be found related to the relationship between horizontal alignment in a roadway segment and speed distributions with remarkably high speed variance.