Number 02/Failure & fragility/Reliability
The Maintenance Ratio
The quantity
The ratio of degradation rate to repair capacity, measured in the same units. Near one, condition hovers and failure is governed by variance; far from one, the system either fails fast or ages negligibly.
01Why it matters
It explains why maintenance budgets predict condition but not failure, and why some neglected assets persist for decades.
02Expected value
Failure hazard should change regime near a ratio of one, independent of age.
03How it would be measured
Degradation from condition monitoring; repair capacity from intervention records. Both exist in most asset registers.
04What would refute it
If hazard depends only on condition, the ratio adds nothing.