Proportion of Stopping Distance (PSD)#
Description#
The PSD metric, proposed by Allen et al., is defined as the distance to a conflict area CA divided by the MSD [Allen1978] [Mahmud2017] [Guido2011] [Astarita2012]. Therefore,
Properties#
Run-time capability#
Yes
Target values#
< 1 (point of no return), 1.5 (scenario classification) [Huber2020]
Subject type#
Road vehicles (automated and human)
Scenario type#
Any scenario with a conflict area (containing a potential intersection point)
Inputs#
CA, position \(p_1\), velocity \(v_1\), maximal deceleration of ego \(a_{1,\mathit{long,min}}\)
Output scale#
\([0, \infty)\), number, ratio scale
Reliability#
Can be reduced if actor tries to bypass conflict area in order to avoid collision, reliability higher than ET [Allen1978]
Validity#
Low, depending on validity of the conflict area; found to have lowest relation to collision history for an unprotected left turn scenario with a static CA [Allen1978]
Sensitivity#
High, assuming that the conflict area is defined as a dynamically changing predicted point of collision [Guido2011], reduced otherwise
Specificity#
Low, if criticality is measured completely independent of other actors in the scenario, also low if defined relative to a predicted collision point [Guido2011]
Prediction model#
Time window#
Unbound, but usefulness depends on DMM
Time mode#
Linear time