Paul St-Aubin edited Methodology.tex  almost 10 years ago

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\item Roundabouts are large enough that they can and often do contain \textbf{multiple independent road user interactions simultaneously}. For example, a motorist approaching the roundabout depicted in Figure~\ref{fig:roundabout-quadrants} from the North-West section can do so independently of any movement occurring inside of the South-East section. This is not strictly true for all interactions however; particular care should be taken at the transitionary zone between sections.  \end{itemize}  These sections are termed \textit{quadrants} as they cut the most common configuration of roundabout, a four-way roundabout, into four sections using two axes of symmetry. Though other configurations do exist, exist and roundabouts are rarely perfectly symetrical in reality,  the general principle still applies: a quadrant is defined as the section of a roundabout delimited by an approach and the next immediate exit, bounding a central weaving zone (depicted in Figure~\ref{fig:roundabout-weaving-zone}) Figure~\ref{fig:roundabout-weaving-zone}, first presented and discussed in \cite{St_Aubin_2013})  where the approach and exit lanes overlap with the lanes of the central ring. In this zone, road users experience the most types of conflicts: rear-end, lane-change (if a multi-lane roundabout), and weaving conflicts. These weaving conflicts are unique to roundabouts and the key aspect of the yielding behaviour that governs right-of-way of the intersection as a whole. Pedestrian-motorist conflicts normally do not overlap with the weaving zone as the cross-walks are normally set back from the roundabout by a couple of car-lengths. Interactions between users, motorists and pedestrians alike, located on an approach and an adjacent exit, and vice versa, can be considered independent from one another as they are normally always separated by a median.