Table 2.

Severity levels of warning messages.

Severity Level (SL)	SL Value	Range of Collision Probability (${\mathit{\rho }}_{\mathit{c}}$)
$S{L}_0$	00	$0.00$<${\rho }_c$⩽$0.33$
$S{L}_1$	01	$0.34$<${\rho }_c$⩽$0.66$
$S{L}_2$	10	$0.67$<${\rho }_c$⩽$1.00$
$NW$	11	${\rho }_c=0.00$