Calibration Of A Method For Selecting
Roundabouts As A Function Of The
Inner Island Treatment
Author(s)
J. Falciani, A. Pratelli, M. Martello & R. Souleyrette
Abstract
It is generally accepted that a driver’s ability to perceive, recognize, and react to
surroundings contributes to safer roads. The objective of this paper is to
investigate the perceptibility of roundabouts as influenced by their most
distinctive feature – the central island treatment. Previous work has shown how
visual perception of central island treatment can improve road safety
performance. Recently, the authors have suggested a roundabout central island
treatment classification scheme with three categories: Reduced, Compressed and
Slender. Classifying roundabout central island treatment types was necessarily
somewhat subjective. This paper introduces a more quantitative measure for
central island visual perception, based on the theory of visual intrusion as
measured by the solid angle subtending the central island treatment. Data were
collected using laser instruments, Google Streetview® and Google Earth®, and
the related solid angles have been estimated for a large sample of roundabouts
located both in Tuscany (Italy) and in the United States. The classification
scheme is analyzed using the nonparametric Fisher's exact test which shows the
central island treatment classification scheme is not associated with roundabout
size. Therefore, central island treatment can be utilized as a unique metric for
categorizing roundabouts. Descriptive statistics indicate that roundabouts with
compressed island treatments have the largest solid angles (and implied
visibility) when compared to either reduced or slender treatments, which have
similar levels of visual intrusion as estimated by their solid angle.
Keywords: roundabout, central island treatment classification, solid angle.
Keywords
roundabout, central island treatment classification, solid angle.
Related Book
Other papers in this volume
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