Innovative Roadside Design Curve of Lateral Clearance: Roadway Simple Horizontal Curves

AbstractThe roadside of horizontal curves should be cleared of any obstructions to satisfy sight distance (SD) requirements. This paper proposes an innovative roadside design curve for the required lateral clearance (offset) on simple horizontal curves. The roadside curve consists of a circular curve connected with two spiral curves and exhibits several advantages: (1) it provides a smooth SD profile that improves design consistency; (2) it has beneficial effects on safety for sharp horizontal curves; and (3) it leads to the development of a simple design aid. The roadside curve provides a good approximation of the required lateral offset for roadway simple horizontal curves with a length lesser or greater than the required SD. The results show that approximately two-thirds of the maximum lateral offset required by the American Association of State Highway and Transportation Officials should be provided at half of the required SD upstream and downstream of simple horizontal curves. The concept of roadside...