Extra hours, extra confusion: Making sense of adverse condition and emergency relief rules
Winter weather brings more than snow and ice, it brings confusion about what rules apply when conditions change. Two of the most misunderstood Hours of Service (HOS) provisions are the Adverse Driving Conditions (ADC) exception and Emergency Relief Orders (EROs). While both can impact how long a driver may operate, they apply in very different situations.
What are adverse driving conditions?
The Federal Motor Carrier Safety Administration (FMCSA) defines adverse driving conditions as weather or road conditions that could not have been known at the time of dispatch. This exception is meant to cover unexpected events, things a driver could not reasonably plan around. If conditions were forecasted, the ADC exception does not apply.
What does the exception allow?
When adverse conditions arise unexpectedly, a driver can drive up to 2 additional hours after the limits have been reached. Extending the driving time does not decrease the rest requirements. The exception cannot be used if the driver would not have been able to arrive on time, under normal conditions.
If a driver begins a trip and several hours into a trip, an unpredicted storm drops visibility, ADC may be used to complete the trip. A blizzard that was in the forecast for several days, would not qualify for this exception because the conditions were predicted in advance.
What is an Emergency Relief Order?
EROs are issued by state or federal authorities during significant events affecting public safety or essential supply chains. These orders temporarily modify HOS rules for drivers providing direct emergency assistance. Common examples of when these orders would be issued in the summer are:
- Widespread freezing temperatures that cause energy shortages,
- Major storms that disrupt supply chains and,
- Emergency transport of essential items like fuel, food and, medical supplies.
What does an ERO allow?
Each order is different, but they may allow:
- Temporary suspension of some or all HOS limits,
- More flexibility for drivers hauling emergency-related freight and,
- Apply across and entire state or region.
EROs should only be used when an official declaration is in place. Time limits are placed on these orders, so it is important to stay informed. The driver must be carrying emergency-related freight and, the carrier should notify the driver when they can and cannot use the exception.
Safety first, safety always
Neither of these exceptions override safety. Even with extra driving time, drivers should make good choices.
- Slow down in snow and ice,
- Increase following distance,
- Stop if conditions become unsafe and,
- Never drive fatigued.
The law gives flexibility in special circumstances, but it never removes the driver’s responsibility to operate safely.
Key to remember: Winter brings unique challenges for commercial drivers, but knowing the difference between Adverse Driving Conditions and Emergency Relief Orders helps ensure you stay safe, legal, and prepared.
















































