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\subsection{Traffic Data Collection}  Video data is collected at a number of sites using purpose-built video data collection systems \cite{Jackson_2013}. \cite{Jackson_2013, St_Aubin_2016_thesis}.  As mentioned earlier, video data at Québec roundabouts was reused from a related road safety project. Complimentary video data was taken at the selected Swedish sites, deploying a similar video data collection system employing two cameras to cover the entire view of the roundabout. The video data is then processed with state-of-the-art computer vision software purpose-built for surrogate safety analysis applications. The open-source software Traffic Intelligence extracts all road user trajectories from image space using feature-based-tracking \cite{Saunier_2006}, providing Cartesian coordinates of all moving objects within a scene thirty times a second. This high-resolution data of all road users within a traffic scene is needed for the road user behaviour analysis to follow. Given the large volume of data to be processed, additional software is used to partially calibrate and automate the analysis and to annotate the traffic scene with contextual metadata \cite{St_Aubin_2015}.