Drowsy driving, also colloquially referred to as fatigued driving happens anytime a driver gets behind the wheel of a vehicle when they are sleepy, or tired and drowsy, and clearly in a sleep deprived state. When a drowsy driver gets involved in an accident that causes a crash, typically that crash is referred to as a drowsy driving crash.
According to the National Highway Traffic Safety Administration drowsy driving is implicated as the cause of over 83,000 vehicle crashes annually. It is also directly responsible for over nearly 1,000 deaths every year. It is important to keep in mind that this doesn't include accidents that are caused by a driver's inattention.
It is also widely accepted that crashes that are caused by drowsy driving are underreported so the figures representing crashes and fatalities are treated as a conservative estimate.
In an effort to combat this problem particularly with truck drivers, the Federal Motor Carrier Safety Administration has been instructed to regulate how long truck drivers can be allowed to operate their trucks on the nation's highways in a manner that is conducive to their, and the rest of the motoring public's, safety. Trucking companies have a financial incentive to maximize the amount of time their trucks are out on the road delivering their payload to their intended destination rather than parked in a truck stop while the driver gets some rest.
In combating drowsy truck driving, the FMCSA issued regulations in late 2011 that were intended to force truck drivers to get the much needed rest their bodies required to operate their trucks safely. Essentially, there were two new requirements that truck drivers had to abide by. The first was that all truck drivers needed to take a minimum 30-minute rest break within, but no later than the initial eight hours of their shift. The second regulation that was implemented was that truck drivers had to take two breaks between 1:00 and 5:00 in the morning, and essentially capped the number of hours that they can be on the road every week from 82 hours to a more reasonable and manageable 70 hours.
Source: National Highway Transportation Safety Administration, "Research on Drowsy Driving," Accessed May 25, 2015