The Federal Motor Carrier Safety Administration performs frequent studies related to large commercial vehicles and safety on the road.

Among their studies is the relationship between driver alertness and time of day. This is where the circadian rhythm becomes a factor.

Affecting response time

Many circumstances create truck driver fatigue, such as extended work hours, strenuous activity or an insufficient amount of sleep. One FMCSA study found that the possibility of an accident is highest in the first hour of driving.

Drivers who sleep in their sleeper berths may be most at risk since they often take to the road shortly after waking. Researchers believe that sleep inertia affects drivers at this particular time. It reduces their vigilance, reaction time and cognitive functioning, leaving room for poor judgment calls and the increased opportunity for a crash.

Understanding the circadian rhythm

Human bodies go through a wake/sleep cycle every day. This involves an internal clock, which controls the level of alertness. People are naturally drowsy between midnight to 6 a.m. and again from 2 p.m. until 4 p.m. Truck drivers must be especially careful since they are often driving during these natural lulls. This corresponds to another FMCSA study, which finds that a driver’s alertness level relates more to time of day than to time on task.

Compounding errors

Truck drivers who feel fatigued may try various ways to recharge, such as turning up the radio, smoking, opening a window or drinking coffee. None of these quick fixes are effective in terms of maintaining alertness. In fact, too much coffee can cause headaches, nervousness, irritability and worst of all, insomnia.

Dealing with consequences

When truckers ignore their bodies’ natural rhythms, they put others at risk of a truck-car crash, in addition to themselves. Usually, it is the people in passenger vehicles that suffer most from these collisions. Although the truck driver may be at fault, the trucking company may also have a role in imposing an unhealthy or illegal schedule that leads to the crash. There may be multiple parties liable if the victim decides to take the case to court.