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