OOS / Out-of-Service Order

Definition

An Out-of-Service Order (OOS) under 49 CFR Part 396 prohibits a driver or vehicle from operating until a specific safety condition is corrected. Issued at roadside inspections by certified inspectors using the North American Standard Out-of-Service Criteria. Vehicle OOS conditions include critical mechanical defects (brake violations, tire wear, lighting); driver OOS conditions include hours-of-service violations and license issues. OOS rates feed the CSA scoring system; persistently high rates trigger interventions. Violating an active OOS order carries civil penalties under 49 USC §521.