deletions | additions       diff --git a/Methodology Flow.tex b/Methodology Flow.tex  index 4c64dbe..af60464 100644  --- a/Methodology Flow.tex  +++ b/Methodology Flow.tex 
...
\subsubsection{Time-to-collision}  Time-to-collision (TTC) is the surrogate measure of safety of choice for its relative maturity, simplicity, and transferability properties. TTC measures the time remaining, at any instant in time before two road users on a potential collision course collide: higher values are better for safety. It does not have the same level of validation in the literature as speed, but while speed is a good predictor of collision severity, TTC promises to be a good predictor of collision probability, a property which is arguably lacking with speed \cite{Hauer_2009}. Therefore, modelling one ant the other should give a good overall representation of of collision risk associated with road user behaviour.  Several collision course modelling techniques are used in the literature, chief amongst them in terms of ubiquity is constant velocity \cite{Laureshyn_2010}. The constant velocity motion prediction model is deemed inadequate for TTC measurement in roundabouts however, as road users in roundabouts rarely follow straight trajectories, both inside the roundabout and on a significant portion of the approach. Fortunately, some more sophisticated naturalistic motion prediction models have been developed to overcome this shortcoming: motion patterns are used for their ability to learn normal movement within a traffic scene. A discretised motion pattern matrix method developed specifically for roundabouts \cite{St_Aubin_2014} is used for this study. We also elect to model all traffic events, using a conservative minimum probability of collision detection of 0.001, and using the indicator aggregation by the 15th percentile unique per user pair as is described in \cite{St_Aubin_2015}. \subsection{Site Selection}