Full moon a danger sign for motorcyclists

motorcycle moon photoPhoto © AdobeStock

Here’s something to think about if you’re a motorcyclist. A study finds that the risk of fatal motorcycle accidents is higher when there’s a full moon.

Why? No one is quite certain and since the study was observational — meaning that it is based on statistical observations — it doesn’t provide an answer but it’s thought that a full moon can be enough of a distraction to lead to accidents. Motorcycle crashes are a common cause of death worldwide. In the United States, they account for nearly 5,000 deaths every year — one in seven total road traffic deaths and $6-$12 billion in costs to society.

The study analyzed data from the official United States registry of motor vehicle crashes from 1975 to 2014, and calculated the number of fatal crashes on full-moon nights compared with control nights (exactly one week before and one week after the full moon).

A total of 13,029 people were in a fatal motorcycle crash during the 1,482 separate nights (494 full moon nights, 988 control nights). The typical motorcyclist was a middle-aged man (average age 32 years) riding a street bike in a rural location who experienced a head-on frontal impact and was not wearing a helmet. Similar results were found in the UK, Canada and Australia.


Overall, 4,494 fatal crashes occurred on the 494 nights with a full moon, equal to 9.10 per night, and 8,535 on the 988 control nights without a full moon, equal to 8.64 per night. This gave an absolute total increase of 226 additional fatal crashes over the study period, meaning for every two full moon nights, there was one additional fatal crash.

The increased risk was even greater under a supermoon. Of the 494 full moon nights, 65 were a supermoon night (where the moon appears larger and brighter than a regular full moon). A total of 703 fatal crashes occurred on a supermoon night, equal to 10.82 per night — about two additional deaths on a night with a supermoon.

The researchers, Donald Redelmeier at the University of Toronto and Eldar Shafir at Princeton University, concluded that the findings highlight the importance of constant attention when riding, and that extra care is needed 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,” they said in a news release announcing the findings. The study was published in the British medical journal BMJ.

About the Author

Truman Lewis
Truman has been a bureau chief and correspondent in D.C., Los Angeles, Phoenix and elsewhere, reporting for radio, television, print and news services, for more than 30 years. Most recently, he has reported extensively on health and consumer issues for ConsumerAffairs.com and FairfaxNews.com.