4T-Roundabout Design

Description The Roundabout Design course provides guidelines for the design, construction, operation and maintenance of roundabouts.
The course begins with the definition of physical features and dimensions. Roundabouts are distinguished from other circular intersections and placed into categories such as mini-roundabouts, urban roundabouts and rural roundabouts. Both single lane and double lane roundabouts are included. Policy considerations are discussed such as multimodal considerations and benefits/costs associated with roundabouts. The planning steps to develop a roundabout are detailed. Areas of concern include number of entry lanes, selection of categories, comparing operations performance of alternative intersection types, space requirements and economic evaluation.
Traffic operation at roundabouts is discussed in terms of capacity and performance analysis. Roundabout safety is discussed in terms of conflicts and crash statistics. Geometric design elements such as design speed, radius and superelevation are defined. Traffic design including signing, pavement marking and illumination are detailed. Landscaping of the central island and splitter islands is discussed.
The course is designed to provide a basic knowledge of Roundabout Design from which a person can use this information in traffic studies and roadway design.
Course Outline This course provides a basic background knowledge of the history, definitions and design of roundabouts. It includes definitions of terms, types of roundabouts and operation, safety and geometric design of roundabouts. Also included are discussions of illumination and landscaping choices.
The different types of circular intersections are discussed. Roundabout features, dimensions and characteristics are also identified. The operation and maintenance cost of roundabouts are covered. In addition, design guidance is provided for the accommodation of pedestrians and large vehicles. Safety is covered as it relates to roundabout capacity, exit capacity and performance analysis.
Geometric design is covered in detail including the design process, speed-curve relationship, design vehicle, non-motorized users, alignment of approaches and entries and geometric elements.
Traffic design is included as it relates to signing, pavement markings, illumination and landscaping.