deletions | additions       diff --git a/subsection_Merging_Zone_The_reasoning__.tex b/subsection_Merging_Zone_The_reasoning__.tex  index a5b29e3..39b8211 100644  --- a/subsection_Merging_Zone_The_reasoning__.tex  +++ b/subsection_Merging_Zone_The_reasoning__.tex 
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  \subsection{Beahavoural Measures}  The parameters of interest for this particular study are the most notable surrogate safety measures: speed (and speed profiles), time-to-collision (TTC) \citep{Hayward_1971}, andyielding  post-encroachment time (yPET). Note that  yPET is an ordinary PET measure \citep{allen1978analysis} but is designated yPET as it is  measured specifically at the merging zone  yield line, where encroachment is prohibited by way of mandated yielding on the part of the approaching road user only. Speed and yPET are measured directly from the observed road user trajectories as they occur.  Speed and yPET are measured directly from the road user trajectories as they occur. TTC, however, requires the modeling makes use  of potential collisions. collision-course prediction models.  Typically, potential collisions are defined as collision courses of collision-course events using  constant velocity, velocity motion prediction,  i.e. ``with movement remaining unchanged'' \citep{Amundsen_1977}. Given the non-linear environment of roundabouts, driving required to navigate the deflection induced by roundabout central islands and approach angles,  a more sophisticated motion collision-course  predictioncollision course  model is used instead. For instead: for  this work, the discretised motion pattern motion prediction model  developped specifically as a result to address the issues  of motion prediction needs modeling movement  in roundabouts complex environments  \citep{St_Aubin_2014} is used. It is be no means specific to roundabouts however. Speed is widely regarded in the literature as a predictor of collision severity \citep[e.g.][]{Fildes_1993, elvik2004speed}. Meanwhile, TTC is one of the most popular surrogate safety measures intended as a predictor of collision probability (as it models near-misses). yPET is of interest as a model of yielding behaviour and merging aggressivity (it is related to gap time and gap acceptance).