ISS Score (Inspection Selection System)
FMCSA's composite 1-100 algorithm for prioritizing carriers at roadside inspections. Higher scores mean higher inspection probability. The insurance industry widely uses ISS as a single-number risk indicator because it synthesizes multiple BASIC dimensions. CarrierOk serves ISS scores via the iss_value API field.
Learn moreWhat is ISS Score?
The Inspection Selection System (ISS) score is FMCSA's algorithm for determining which motor carriers should be prioritized for roadside inspection. ISS scores range from 1 to 100, with higher scores indicating that the carrier is more likely to be selected for inspection based on its safety profile. The score is computed from a carrier's BASIC percentiles, out-of-service rates, and other safety data points, effectively synthesizing the full SMS picture into a single number. ISS scores are used by law enforcement at weigh stations and during roadside encounters to decide whether to inspect a vehicle — a truck from a carrier with an ISS of 90 will almost always be pulled in, while a truck from a carrier with an ISS of 15 will typically pass through. Beyond its FMCSA enforcement purpose, the ISS score has been widely adopted by the trucking insurance industry as a composite risk indicator. Underwriters use ISS as a quick screening tool because it captures multiple safety dimensions without requiring them to evaluate each BASIC individually. Common risk tiers: scores 1-50 are generally considered acceptable, 50-75 warrant additional review, and 75+ are often auto-declined. CarrierOk provides ISS scores via the iss_value field alongside all underlying BASIC data.
Why does iss score matter?
Insurance Underwriters
ISS is the most widely used single-number safety screen in trucking insurance — carriers above 75 are typically declined or referred to specialty markets, while scores below 50 qualify for standard programs.
Freight Brokers
A carrier with a high ISS score will be stopped and inspected more frequently, leading to transit delays — and if the inspection reveals violations, the truck could be placed out of service mid-route.
Developers & Platforms
The iss_value field is the easiest risk gate to implement — a single integer comparison replaces the need to evaluate 7 BASIC percentiles individually for basic risk screening.
Key values & thresholds
| Category | Value |
|---|---|
| Score Range | 1 – 100 |
| Low Risk | 1 – 50 |
| Moderate Risk | 50 – 75 |
| High Risk | 75 – 100 |
| Input Data | BASICs, OOS rates, safety data |
ISS Score in the CarrierOk API
This data is available via the /v2/profile endpoint. The following fields are returned in the carrier profile:
/v2/profileiss_valuebasic_percentile_unsafe_drivingbasic_percentile_crash_indicatorrisk_factors_scoreFrequently asked questions
What is a good ISS score for a trucking company?
Lower is better. Scores from 1-50 are generally considered acceptable for standard insurance programs and indicate the carrier is performing better than average. Scores from 50-75 warrant additional review and may result in higher premiums. Scores above 75 are considered high-risk — most standard insurance programs will decline carriers in this range, and they face frequent roadside inspections.
How is the ISS score calculated?
FMCSA computes the ISS score from a carrier's BASIC percentile scores, out-of-service rates, and other safety data. The exact formula is not publicly disclosed, but it effectively synthesizes the full Safety Measurement System picture into a single 1-100 number. Carriers with multiple elevated BASICs will have higher ISS scores than carriers with a single elevated category.
What is the difference between ISS score and BASIC percentiles?
BASIC percentiles are category-specific scores across seven safety dimensions (Unsafe Driving, HOS, Vehicle Maintenance, etc.). The ISS score is a single composite number that synthesizes multiple BASICs and other safety data into one risk indicator. Think of BASICs as the detailed breakdown and ISS as the summary grade. Both are valuable — ISS for quick screening, BASICs for understanding what's driving the risk.
Related terms
BASIC Percentile
A 0-100 peer-relative safety score across seven FMCSA categories: Unsafe Driving, HOS, Vehicle Maintenance, Controlled Substances, Driver Fitness, Hazmat, and Crash Indicator. Higher is worse. CarrierOk computes all 7 BASICs including the two FMCSA withholds from public view.
CSA (Compliance, Safety, Accountability)
FMCSA's enforcement and compliance program that uses the Safety Measurement System to identify and prioritize high-risk motor carriers for intervention. CSA drives BASIC percentile scores, warning letters, and compliance reviews. CarrierOk provides all 7 BASIC percentiles, alert flags, and historical trend data via API.
OOS Rate (Out-of-Service Rate)
The percentage of a carrier's roadside inspections that result in an out-of-service order, meaning the driver or vehicle is prohibited from operating until the violation is corrected. National average vehicle OOS rate is approximately 21%. CarrierOk provides both driver and vehicle OOS rates and flags carriers exceeding national averages.
SMS (Safety Measurement System)
FMCSA's quantitative system for measuring motor carrier safety performance using inspection, crash, and investigation data. SMS produces the BASIC percentile scores that underpin the CSA enforcement program. CarrierOk computes all 7 BASIC percentiles from SMS source data and updates more frequently than FMCSA's monthly cycle.
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