Adverse Driving Conditions

The adverse driving conditions exception under FMCSA Part 395.1(b) allows commercial motor vehicle drivers to extend their maximum driving time by up to 2 hours when they encounter unexpected adverse conditions that were not known or could not have been reasonably anticipated before the trip began. This means a property-carrying driver may drive up to 13 hours instead of the standard 11 hours.

Qualifying adverse conditions include snow, ice, sleet, fog, severe wind, unusual road conditions such as highway closures or major construction, and abnormal traffic congestion that was not foreseeable. The key requirement is that these conditions must be encountered after the driver has begun driving and could not have been known before the trip started. Conditions that were forecasted before departure do not qualify.

Under the 2020 HOS rule update, the adverse driving conditions exception was expanded to also extend the 14-hour driving window by 2 hours, in addition to the 2 extra driving hours. This change addressed a practical limitation of the previous rule, where drivers could use the extra driving hours but still ran up against the 14-hour window. Drivers must document the adverse conditions on their ELD when invoking this exception.