A full moon may spell extra danger for motorcyclists, a new study suggests.

Momentary distractions are a common cause of crashes. Because a full moon can be a major distraction and occurs about 12 times a year, researchers decided to investigate whether full moons might be linked to more motorcyclists’ deaths.

“Glancing at the full moon takes the motorcyclist’s gaze off the road, which could result in a loss of control,” explained study author Donald Redelmeier, a professor at the University of Toronto’s department of medicine.

The average motorcycle ride is more dangerous than a drunk driver with no seatbelt traveling the same distance, he added.

“Because of this, we recommend riders and drivers orient their attention, ignore distractions, and continuously monitor their dynamic surroundings,” he said.

In the study, the researchers analyzed data on just over 13,000 fatal motorcycle crashes that occurred in the United States from 1975 to 2014. Of those, 4,494 occurred on 494 nights with a full moon and 8,535 on 988 nights without a full moon.

That worked out to 9.1 fatal crashes on nights with a full moon and 8.6 fatal crashes on nights when the moon wasn’t full. For every two full moon nights, there was one additional fatal crash, according to the report, published Dec. 11 in the BMJ.

“While these figures might seem low on the surface, they are quite significant,” Redelmeier said. “All of these deaths could have been prevented completely by [a] small difference in behavior.”

Data from Canada, Great Britain and Australia revealed similar patterns, according to Redelmeirer and colleague Eldar Shafir, from Princeton University.

The typical victim was a middle-aged man riding a street bike with a large engine in a rural area. Most suffered a head-on crash, and less than half were wearing a helmet, the researchers found.

The risk was greatest on a supermoon night. That’s when a full moon appears larger and brighter than a regular full moon. There were 703 fatal crashes on 65 supermoon nights, or 10.8 per supermoon night. For every supermoon night, there were about two additional deaths.

Because this is an observational study, no firm conclusions can be made about cause and effect, the researchers noted. They also did not take into account other distractions or traffic hazards.

However, they said their findings highlight the need for constant attention when riding a motorcycle, and the need for extra care when riding during a full moon.

“Additional strategies while riding might include wearing a helmet, activating headlights, scanning the road surface for defects, respecting the weather, being wary of left-turning vehicles, obeying traffic laws and forgoing stunts,” Redelmeirer said in news releases from Princeton and the BMJ.

Each year, nearly 5,000 people die in motorcycle accidents in the United States. These fatal accidents account for one in seven of all road traffic deaths and $6 billion to $12 billion in costs to society, according to the study.

More information

The U.S. National Highway Traffic Safety Administration has more on motorcycle safety.