Tactical Maintenance: The maintenance tactic whereby a corrective maintenance task is executed at predetermined intervals of usage (mileage, tonnage, hours, batches, events etc.) to prevent unacceptable failure consequences before they occur. Usage Based maintenance is only effective if there is age determination or a definite pattern in the occurrence of failures (reliable operational period - statistically determinable, before most failure will happen). Example: Typical car timing belt - will normally operate reliably and will be replaced after 80 000km (example). This approach is normally taken if there is no mechanism to determine deterioration in function, and if there are no safety consequences, or unacceptable environmental or economical consequences.