Night shift workers are at greater risk of a crash when driving home from work than day shift workers according to new research conducted by Brigham and Women’s (B&W) Hospital in Boston. The study’s results were published this month in the Proceedings of the National Academy of Sciences.

It has long been known that shift workers, especially those whose shifts rotate between day and night are at greater risk for health problems, including heart attacks. The researchers at B&W felt that night shift workers might suffer a greater risk of involvement in a motor vehicle crash because, no matter how long they had worked the night shift, their natural circadian rhythms were disrupted, preventing them from getting adequate sleep.

Driving drowsy is a major problem among American drivers. According to an American Automobile Association (AAA) study published last year, approximately 6,400 people are killed in 328,000 crashes per year due to drowsy driving. According to the AAA study, drowsy driving was responsible for 21 percent of crashes in which a person was killed and 13 percent of crashes in which a person was hospitalized.

 To conduct the research, the researchers recruited night shift workers to drive over a two hour period during daytime immediately following their night shift. The same workers were tested again after getting an adequate night’s sleep. The tests were conducted on a closed test track at the Liberty Mutual Research Institute for Safety.

• During the tests conducted after a night shift, track safety observers had to step in and use emergency braking procedures to prevent a crash in 37.5 percent or one-third of the test drives.
• In 43.8 percent of the test drives, safety observers had to halt the drive prematurely because the test subjects were too sleepy to maintain adequate control of their vehicle.
• Episodes of microsleep (nodding off for three or more seconds) increased with each half hour of the drive.
• Instead of making multiple small-scale steering corrections, subjects made infrequent large-scale steering maneuvers to avoid crossing over into other lanes.
• When tests were conducted after subjects had slept all night, there were no emergency braking interventions or test terminations by the safety observers.

Most of the near crashes and inability to maintain control happened after more than 45 minutes into the two hour drive. The researchers realized that that was a long time but noted that many night shift workers routinely commute more than an hour each way to and from work.

The researchers felt that the safest way to resolve the problem is for employers to provide transportation from the workplace to a central area where night shift workers can get public transportation for the remainder of the trip home.

Read more: High drowsy driving crash risk on daytime commute after night work