What is the adverse driving conditions exception?

Federal hours-of-service rules permit commercial motor vehicles drivers to exceed the normal driving and on-duty limits when they encounter unexpected adverse weather or traffic conditions. Specifically, they are allowed to exceed the 10- or 11-hour driving limit and the 14- or 15-hour duty limit by no more than 2 hours, to make up the time (or part of the time) that was lost.

An absolute prerequisite for use of the adverse-conditions exception under 395.1(b) is that the trip involved must be one that could normally and reasonably have been completed without a violation and that the unforeseen event occurred after the driver began the trip. Adverse-driving conditions include snow, sleet, fog, other adverse weather conditions, or unusual road and traffic conditions, which were not known, or could not reasonably be known, to a driver immediately prior to beginning the duty day or immediately before beginning driving after a qualifying rest break or sleeper-berth period, or to a motor carrier immediately prior to dispatching the driver. it does not apply to such situations as a driver’s desire to get home, shippers’ demands, market declines, shortage of drivers, or mechanical failures.