New Moon Deadly to Nighttime Walkers

If you enjoy walking in the moonlight, check to be sure the moon is actually out first. Researchers at the University of Michigan Transportation Reserach Institute (UMTRI) found that walking under a new moon, when the night is darkest, is more dangerous than under a full moon, when the bright satellite lights the way.

Michael Sivak, Brandon Schoettle, and Omer Tsimhoni examined nighttime traffic fatalities in crash data from 1996 to 2005. They found that the mean number of pedestrian fatalities during this time was 22 percent higher on nights with a new moon compared to nights with a full moon.

"The overall nighttime road fatality rate per distance traveled in the United States is about three times the daytime rate, due mostly to lower ambient illumination and higher frequencies of fatigued, intoxicated and younger drivers," said Sivak. "In this study, we found that pedestrian crashes are sensitive to differences within low levels of ambient illumination, which can vary in nighttime conditions."

Could there be some connection between the amount of moonlight and the condition of drivers? Are people driving at night under a new moon more tired? Have they drunk more alcohol? Do more young people drive during a new moon?

If any of the above are true, then the light from the moon itself may not be the cause of the higher fatality rate for pedestrians walking on nights with a new moon. Research hasn't been done to test if there's a correlation, but Sivak doesn't think there is one. "The differences in the ambient illuminance for nights with a full moon versus a new moon are unlikely to be correlated with any other factors that are known to influence the likelihood of nighttime pedestrian crashes....Consequently, the results imply that the amount of moonlight has substantial influence on pedestrian crashes."

In another, preliminary, study, David Gerard and Paul Fishbeck of Carnegie Mellon University found a 186% jump in vehicle-pedestrian accidents in the month of November -- focused around the hour of 6 PM. Just as with the UMTRI study, the root cause was lack of illumination. November is when Daylight Savings ends, and drivers unaccustomed to the sun going down before 6 PM are less cautious around that time than they should be. Gerard and Fishbeck back up their findings by noting that pedestrian fatalities then drop 21 percent in December, which indicates that people are adjusting to the different daylight hours.

Gerard and Fishbeck analyzed their data with the trafficSTATS system, a joint effort between the AAA Foundation for Traffic Safety and Carnegie Mellon University. They don't plan to officially publish or peer-review their findings.