HOS (Hours of Service)
Federal regulations limiting commercial driver operating hours to prevent fatigue-related crashes. Key limits include 11 hours driving, 14 hours on-duty, and mandatory 30-minute breaks. HOS violations are one of the 7 BASIC categories tracked in CarrierOk's BASIC percentile data.
Definition
Hours of Service (HOS) regulations are federal rules under 49 CFR Part 395 that govern how long a commercial motor vehicle driver may operate before mandatory rest. The rules exist to prevent fatigue-related crashes, which FMCSA data shows are a leading factor in commercial vehicle accidents. Key HOS limits for property-carrying vehicles include: an 11-hour driving limit after 10 consecutive hours off duty; a 14-hour on-duty window (driving must occur within 14 hours of coming on duty); a mandatory 30-minute break after 8 cumulative hours of driving; and a 60/70-hour weekly limit (no driving after 60 hours on duty in 7 days or 70 hours in 8 days, with a 34-hour restart provision). Passenger-carrying vehicles have different limits. HOS compliance is monitored through Electronic Logging Devices (ELDs) and verified during roadside inspections. Violations are recorded in FMCSA's inspection database and flow into the Hours-of-Service BASIC percentile calculation. Chronic HOS violations indicate a carrier is either pushing drivers beyond safe limits or has inadequate dispatch practices — both strong predictors of fatigue-related crashes. CarrierOk surfaces the HOS BASIC percentile, underlying measures, and alert flags via the basic_percentile_hours_of_service field.
Why It Matters
For Underwriters
Elevated HOS BASICs are a leading indicator of fatigue-related claims — carriers above the 65th percentile in HOS are in FMCSA's intervention territory and represent measurably higher crash risk.
For Brokers
A carrier with chronic HOS violations may miss delivery windows due to mandatory rest stops, or worse, push drivers to violate rules on your loads — creating direct negligent selection exposure.
For Developers
Use basic_percentile_hours_of_service and basic_alert_hours_of_service as inputs to fatigue-risk models — these are ELD-validated data points that reflect actual compliance behavior, not self-reported data.
Key Values
| Max Driving Time | 11 hours (after 10 hrs off) |
| On-Duty Window | 14 hours |
| Mandatory Break | 30 min after 8 hrs driving |
| Weekly Limit (7-day) | 60 hours on duty |
| Weekly Limit (8-day) | 70 hours on duty |
| Restart Provision | 34 consecutive hours off duty |
In the API
/v2/profileRelated Fields
basic_percentile_hours_of_servicebasic_alert_hours_of_servicebasic_measure_hours_of_serviceFrequently Asked Questions
What are the HOS rules for truck drivers?
For property-carrying CMV drivers: maximum 11 hours driving after 10 consecutive hours off duty, all driving must occur within a 14-hour on-duty window, a 30-minute break is required after 8 cumulative hours of driving, and drivers cannot exceed 60 hours on duty in 7 days or 70 hours in 8 days. A 34-hour restart provision resets the weekly clock. Passenger-carrying drivers have different limits.
What happens if a truck driver violates HOS rules?
HOS violations detected during roadside inspections are recorded in FMCSA's database and can result in the driver being placed out of service until they've had adequate rest. Repeat violations accumulate in the carrier's Hours-of-Service BASIC percentile. Carriers with BASICs above the 65th percentile face FMCSA intervention, and severe or willful violations can result in fines up to $16,000 per violation.
How are HOS rules enforced?
Primary enforcement is through ELDs (Electronic Logging Devices), which automatically record driving time and are checked during roadside inspections. Law enforcement can review ELD data on-screen or via wireless transfer. Violations are entered into the inspection record and flow into FMCSA's Safety Measurement System. FMCSA also conducts targeted investigations of carriers with elevated HOS BASIC percentiles.
Related Terms
ELD (Electronic Logging Device)
A device installed in commercial motor vehicles that automatically records driving time and hours of service. ELDs replaced paper logbooks and are mandated by FMCSA for most interstate carriers since December 2019. HOS violations captured by ELDs feed directly into a carrier's BASIC percentile scores tracked by CarrierOk.
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.