Final answer:
The question is about the maximum on-duty hours a commercial vehicle driver is allowed before they must take a break, which is 14 hours. The 14-hour limit is a standard set by the FMCSA and includes all work-related activities.
Step-by-step explanation:
If we assume the question refers to hours of service regulations for commercial vehicle drivers, such as truck drivers, the most common standard in the United States, under the Federal Motor Carrier Safety Administration (FMCSA), is that a driver is allowed to be on-duty for a maximum of 14 consecutive hours before they are not allowed to drive. However, the driver can only drive for a total of 11 hours during the 14-hour period, after which a 10-hour off-duty period is required.
In the context of the original question, the correct answer, therefore, is d) 14 hours. The 14-hour on-duty limit includes all work-related activities, not just driving time. After reaching the maximum on-duty hours, the driver must then have a rest period before returning to work.
Meanwhile, regarding the potential effects of such on-duty hours on driver performance, it's important to note that sleep deprivation can greatly impair one's ability to drive safely. The experiment mentioned with professional drivers highlights the detrimental effects of sleep deprivation, a key factor to consider alongside regulations for on-duty hours.