Roundabout perception: review of standards and guidelines for advanced warning

This paper deals with roundabout visibility and perception design requirements, including available standards and guidelines in the US and Europe for warning signs. To provide for highest levels of safety, visual perception of junctions is important even where advance warning signs are provided, to reinforce driver knowledge and confidence in their actions. For roundabouts, three different types of central island development are recently suggested to affect their visual perception, and the related classification defines the reduced, the compressed and the streamlined, or slender, central island development. The paper proposes new methodologies to test this perceptibility of various roundabout designs and developments. Two research strategies based on the specific roundabout visual intrusion defined by the solid angle are outlined: on-site stand-by/2D and virtual video/3D. Finally, some preliminary results are discussed in view of selecting original and proper standards. Moreover, future research is suggested for extending the methodology to more comprehensive application.