Vital

Equipment whose correct operation is essential to the integrity of the
Signalling SystemA series of electrical, electronic, electro-mechanical units brought together to form a system which controls the safe movement of trains. More. Most vitalEquipment whose correct operation is essential to the integrity of the Signalling System. Most vital equipment is designed to Fail-Safe principles – a Wrong S... More equipment is designed to Fail-SafeA design philosophy which results in expected failures maintaining or placing the equipment in a safe state. More principles
– a Wrong Side FailureA failure that results in the protection provided by the Signalling System being reduced or removed. See Protected Wrong Side Failure and Unprotected Wrong Side... More of vitalEquipment whose correct operation is essential to the integrity of the Signalling System. Most vital equipment is designed to Fail-Safe principles – a Wrong S... More equipment could directly endanger rail traffic.
See Safety CriticalDirectly influencing safety (when applied to equipment or systems). More.