Roundabout Geometric Design
Designing the geometry of a roundabout involves choosing between trade-offs of safety and capacity. Roundabouts operate most safely when their geometry forces traffic to enter and circulate at slow speeds. Horizontal curvature and narrow pavement widths are used to produce this reduced-speed environment.
Conversely, the capacity of roundabouts is negatively affected by these low-speed design elements. As the widths and radii of entry and circulatory roadways are reduced, the capacity of the roundabout is also reduced.
Furthermore, many of the geometric parameters are governed by the maneuvering requirements of the largest vehicles expected to travel through the intersection. Thus, designing a roundabout is a process of determining the optimal balance between safety provisions, operational performance, and large vehicle accommodation.
This course presents the fundamental design principles common among all roundabout types. This course also presents detailed design considerations specific to multilane roundabouts, rural roundabouts, and mini-roundabouts.
This online PDH course is applicable to traffic engineers, transportation planners, managers, and other technical professionals who are involved in the geometric design of roundabouts.
This continuing education course is intended to provide you with the following specific knowledge and skills:
- Familiarizing with the different types of roundabouts
- Understanding the geometric elements
- Learning the general design principles
- Selecting the appropriate inscribed circle diameter
- Designing the alignment of approaches
- Designing entry and exit curves
- Designing the central and splitter islands
- Determining the stopping and intersection sight distances
- Designing methods to avoid vehicle path overlap
In this course, you need to review Chapter 6, "Geometric Design", of the Federal Highway Administration Publication FHWA-RD-00-067, "Understanding Roundabouts" provided below.
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