Understanding Your ISS Score
Your ISS (Inspection Selection System) score is a single number from 1 to 100 that tells roadside inspectors how likely your carrier is to have safety problems. The lower your score, the better.
What Your Score Means
| ISS Range | What It Means | Inspection Likelihood |
|---|---|---|
| 1-49 | Pass | You usually get waved through at weigh stations |
| 50-74 | Optional | Inspectors may decide to pull you in |
| 75-99 | Inspect | You will likely be pulled for inspection |
| 100 | Out-of-Service | Your operations are halted until the issue is resolved |
What Goes Into Your Score
FMCSA calculates your ISS using several pieces of information:
- Your 7 BASIC scores; These track different types of safety violations. See the BASIC Scores guide for a full breakdown.
- Your carrier type; Passenger carriers, hazardous materials haulers, and general freight carriers are measured differently.
- Your fleet size; Smaller fleets are compared against other small fleets, not against national giants.
- Out-of-Service Orders; If you have an active OOS order, your ISS is locked at 100.
What Is an Out-of-Service Order?
An Out-of-Service (OOS) Order is a federal order that stops your carrier from operating. It is issued when FMCSA finds your operations pose an imminent hazard to public safety. Until you resolve the underlying issues and FMCSA lifts the order, your ISS score stays at 100 and you cannot legally operate.
What Is "Insufficient Data"?
If your carrier is new or very small, FMCSA may not have enough roadside inspection data to calculate a reliable percentile. The specification identifies four scenarios: Case 1A: the carrier is one inspection away from having enough data on a roadside criterion (1-away); Case 1B: the carrier is one away on a driver-inspection criterion; Case 2: the carrier has zero inspections on record; Case 3: the carrier has some inspections but still below the minimum. In all four cases the carrier is flagged "Insufficient Data" and excluded from the ISS ranking. Running more miles and accumulating clean inspections is the path to an assessed ISS.
What Is a BASIC?
BASIC stands for Behavior Analysis and Safety Improvement Category. FMCSA tracks seven categories of safety behavior; things like speeding, vehicle maintenance, and hours-of-service compliance. Each BASIC gets its own percentile score. Your ISS score is built from how many of your BASICs are flagged and how serious they are.
How FMCSA Ranks You
FMCSA does not compare every carrier against every other carrier directly. Instead, it groups carriers into 13 categories based on which BASICs are flagged and how many. Note: Group 6 (Insurance/Other Serious Violations) is derived from investigation findings (revoked authority, missing BIPD coverage, or rejected insurance forms) rather than from BASIC percentile scores. Then it ranks your carrier within that group. This is why fixing even one BASIC can sometimes drop your ISS significantly; it may move you into a different group entirely.
How to Improve Your Score
- Address violations promptly. Pay fines, fix equipment, and retrain drivers.
- Request DataQ corrections. If a violation was entered incorrectly, challenge it through FMCSA's DataQ system.
- Increase inspection exposure. If you have insufficient data, running more miles with clean inspections helps build a track record.
- Resolve OOS orders immediately. Contact FMCSA and comply fully with their requirements to lift the order.
- Stay current on maintenance. Preventive maintenance is cheaper than violations and downtime.
Your ISS score is not permanent. It updates monthly as new inspection data comes in and old data ages out. Small, consistent improvements add up over time.
Heads-Up: FMCSA Is Redesigning the System
FMCSA has approved a major redesign of the Safety Measurement System but it is not yet in effect. The current methodology (v3.20, September 2025) is what FMCSA uses to prioritize carriers today, and it is what this report follows. When the redesign goes live, you will see "compliance categories" instead of "BASICs", Controlled Substances/Alcohol folded into Unsafe Driving, Vehicle Maintenance split into two categories (driver-observable vs mechanic-detected), simpler severity weights, and adjusted thresholds for Driver Fitness and Hazardous Materials. FMCSA has not announced a go-live date. This report will be updated to the new methodology only after FMCSA publishes the final specification and the production data starts using the new structure. See How we built this §7 for the full breakdown.
Sources: FMCSA ISS Algorithm Specification (FMCSA, pp. 9, 14, 16-17); FMCSA SMS Methodology v3.20.
See also: How we built this: a plain-English walkthrough of FMCSA's 14-step ISS recreation, including the Insufficient Data Cases and Group 6.