Conflict Severity (CS)#
Description#
CS is concerned with solely estimating the severity of a potential collision in a scenario [Bagdadi2013]. It thus presents as a suitable factor that can enhance various collision probability metrics in ensuring a more accurate representation of criticality. From the perspective of an actor \(A_1\) performing a braking maneuver at time \(t_\mathit{evasive}\), it is defined as
Thus, it compares the (extended) \(\Delta v\) at time of the evasive maneuver against the \(\Delta v\) at the potential collision point as predicted by TTA if \(A_1\) conducts an emergency braking, assuming \(v_2(t_\mathit{evasive} + \mathit{TTA}(A_1, A_2)) = 0\). CS factors in the relative mass difference due to the correlation between severe injuries and fatality outcome, measured on the Abbreviated Injury Scale, and the mass ratio of the involved actors [Evans1994].
Properties#
Run-time capability#
No, as TTA can only be computed once evasive maneuver has been identified
Target values#
Case study on manually labeled critical scenarios identified a mean CS of \(3.19 \pm 3.7\) m/s, but severity is dependent on speed and type of actors [Bagdadi2013]
Subject type#
Any two actors, also suitable for VRUs
Scenario type#
Any scenario for which a TTA can be determined
Inputs#
\(v_1(t_\mathit{evasive})\), \(v_2(t_\mathit{evasive})\), \(m_1, m_2\), \(\mathit{TTA}(A_1, A_2)\), \(a_{1,\mathit{min}}(t_\mathit{evasive})\)
Output scale#
\((-\infty,\infty)\), velocity (m/s), ratio scale
Reliability#
Comparable to TTA
Validity#
High validity for severity estimation inside scenario type of TTA, as indicated by empirical analysis against a traffic conflict technique, specifically for actors with different masses [Bagdadi2013]
Sensitivity#
Medium, as for critical scenarios where no evasive maneuver is identified, CS returns no value
Specificity#
Comparable to TTA, but increased due to consideration of severity
Prediction model#
Depends on prediction model of TTA