Table 1. Legend of the safety barriers considered in UKAB reports for cause assessment, together with the abbreviations used in Figure 1.

Barrier	Abbreviation
GROUND ELEMENTS
Regulations, Processes, Procedures and Compliance	Procedures&ComplianceG
Manning & Equipment	Manning&EquipmentG
Situational Awareness of the Confliction & Action	AwarenessG
Electronic Warning System Operation and Compliance	WarningG
FLIGHT ELEMENTS
Regulations, Processes, Procedures and Compliance	Procedures&ComplianceF
Tactical Planning and Execution	TacticalPlanningF
Situational Awareness of the Conflicting Aircraft & Action	AwarenessF
Electronic Warning System Operation and Compliance	WarningF
See & Avoid	See&AvoidF