Encroachment Time (ET)#
Description#
The ET metric, proposed by Allen et al. [Allen1978], measures the time that an actor \(A_1\) takes to encroach a designated conflict area CA, i.e.
While the value of ET is loosely correlated with criticality, it completely ignores the dynamics and behavior of any other involved actor.
Properties#
Run-time capability#
No
Target values#
None found
Subject type#
Road vehicles (automated and human)
Scenario type#
Any scenario with a conflict area (containing a potential intersection point
Inputs#
CA, \(t_{\mathit{entry}}(A_1,\mathit{CA})\), \(t_{\mathit{exit}}(A_1,\mathit{CA})\)
Output scale#
\([0,\infty)\), time (s), ratio scale
Reliability#
Low, changes in criticality are reflected marginally in ET, repetition on multiple days showed high measurement variance [Allen1978]
Validity#
Low, as only one actor is considered; validation against historical collision records was performed on one intersection, but results were not significant [Allen1978]
Sensitivity#
Low, as the validity of the metric is low and no target values exist
Specificity#
Low, as the validity of the metric is low and no target values exist
Prediction model#
None, since a-posteriori