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Paul St-Aubin edited section_Methodology__.tex
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\section{Methodology}
\subsection{Site Selection}
Roundabout data for Québec was taken from a related road safety project \cite{St_Aubin_2013}. The pool of data covers roughly 20\% of Québec's 110 roundabouts (at the time of study) with uniform land use, geometric design, and regional representation.
In Sweden, four roundabouts were selected to complement the existing Québec data. These roundabouts were selected on the basis of similarity in geometric design and land use with typical Québec roundabouts. This typical design is characterised by a single lane (on the approach, exit, and ring, each), an approach speed limit of 50 km/h, an outside radius of 12-22 meters, very-low to medium urban density, suburban or commercial land use, moderate visibility over the centre island, and with pedestrian crosswalks. Québec roundabout signalisation is functionally identical to Swedish design, though differs in aesthetics. The Swedish roundabouts chosen were all located in the Skåne province, near the city of Lund.
One important distinction between the Québec and Swedish roundabouts are the pedestrian and, especially, cyclist flows. Cyclist flows in the Québec roundabouts are virtually non-existent; however these flows are non-trivial at many, but not all Swedish roundabouts. Consequently, only Swedish roundabouts with limited pedestrian or cyclist flows were considered for this study (low pedestrian and cyclist flows are still very common in low-density roundabouts). It's also worth noting that besides aesthetic differences the design of the Swedish roundabouts has one vital difference with Québec roundabouts: virtually all sidewalks integrate a cycle lane.
\subsection{Analysis Zone}
At each Swedish roundabout, two cameras were positioned in such a way to cover the entire roundabout completely, and to cover at least one merging zone in each camera completely. The use of analysis zones as units of study instead of roundabouts as a whole is that, while many factors such as land use are shared, many more are not. This includes flows and flow ratios especially, but may also include geometric factors such as lane configuration, signalisation, presence of a crosswalk, approach angle, etc. which can vary from one merging zone to the next even within the same roundabout \cite{St_Aubin_2013}. Studying merging zones individually also better encapsulated the microscopic nature of the data being collected and analysed: roundabouts are often large enough for road user interactions on different sides of the roundabout to occur independently.
