147 Weakest Link

An element designed to fail in order to protect more important elements from harm.

• Weakest links work in two ways: halting systems when they fail (e.g., electrical fuse), or activating mitigation systems when they fail (e.g., fire suppression system).

• Properly designed, the weakest link in a chain is the most important link.

• Weakest links predictably and reliably fail first.

• Weakest links are applicable to systems with cascading fault conditions—i.e., when there is a chain of events that can be interrupted.

• Consider adding weakest links to systems where failures occur as cascading events. Test and verify that weakest links only fail under the appropriate, predefined failure conditions.

See Also Errors • Factor of Safety • Feedback Loop Modularity • Redundancy

Crumple zones are one of the most significant automobile safety innovations of the twentieth century. The front and rear sections of vehicles are designed to crumple in a collision, reducing the energy transferred to the passenger shell.