deletions | additions       diff --git a/Methodolofy Measurement Definitions.tex b/Methodolofy Measurement Definitions.tex  index ac71c91..89b5c57 100644  --- a/Methodolofy Measurement Definitions.tex  +++ b/Methodolofy Measurement Definitions.tex 
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An interaction quantifies the spatial relationship between moving objects in a scene, as is depicted in Figure~\ref{fig:conflict-video}. At the most fundamental level, an interaction is defined as a pair of moving objects simultaneously present in a scene over a common time interval (also referred to as a user pair). We further define an instantaneous observation (i.e. in a given video frame) within this time interval as an interaction instant \cite{St_Aubin_2015_TRBa}.  This interaction definition is generic, if not naive, as the quality depends largely on how the scene is constructed. For example, the significance of an interaction between two vehicles separated from each other physically (e.g. via a median or a building) may not be comparable to an interaction between two vehicles merely separated by lane markings because of the implication that they may  cross the lane marking intentionally or inadvertently very easily. This may interfere with collision prediction attempts, particularly if scenes are not consistently selected and geometry is not controlled. One solution is to perform a triage of user pairs based on physical access and proximity. A network topology coupled with a driving distance horizon is proposed. This is not a perfect solution, however, as physical access may not necessarily be a discrete choice. For the example of the median, it is still physically possible, although much less likely, for a vehicle to cross over into oncoming traffic.