Fatal traffic accidents increase by about 30% in the days around a total eclipse.

For the vast majority of human history, the spectacle of a solar eclipse was clearly terrifying. Cultures around the world have strikingly similar mythologies around the celestial event. Chinese writings describe a dragon eating the sun.

Norse mythology suggests the sun was being consumed by a great sky wolf, and the Incas thought their sun god had been attacked by a Jaguar.

In all these cases, eclipses were a bad omen – a sign that the ruler would soon die, or a war would break out, or famine would come. It was sometime in the 5th century BC that the first human was documented to predict an eclipse – that’s the Greek astronomer Thales of Miletus, according to Herodotus.

Anaxagoras theorized a solar eclipse was caused by the moon’s shadow around a century later, though his geocentric view of the event was off. We would need Copernicus and Kepler before the real orbits were understood.

And so, just as our understanding of the science of lightning changed the experience of a thunderstorm from one of terror to one of awe, our experience of an eclipse has also been changed. We do not fear what will happen on April 8th of this year – when a total eclipse of the sun will pass over much of the country - but, according to a new study, perhaps we should.

200 million Americans live within driving distance of the path of the Total Solar Eclipse that will cross over the bulk of our country in early April. And I, like many of those 200 million, will be getting on the road to position myself somewhere along that path of totality. Side note – I thought I was being clever by calling a ranch in Texas to reserve a spot about a year ago – they told me they had been booked solid for at least three years. Damn you, Kepler.

The reason we are talking about the Eclipse on Impact Factor, nominally a venue for medical commentary is, well, because they are incredibly cool and it is nice to take a break from the usual randomized trials and tribulations, but also because of this study, appearing as a research letter in JAMA Internal Medicine.

Researchers Donald Redeliver and John Staples were worried about the risk of traffic accidents during the upcoming eclipse. How to understand the risks? Well, we can turn to history. And we don’t need Herodotus for this one.

On August 21, 2017 – the shadow of the moon traced this path across the US, coming within three hours driving distance of 1/3rd of the US population.

Using data from the National Highway Traffic Safety Administration Fatality Analysis Reporting System, researchers evaluated whether fatal traffic accidents increased during the eclipse period. Now – to be fair – the maximum duration of this particular eclipse was 2 minutes and 42 seconds in Carbondale, Illinois. It would be really hard to study the risk of traffic fatalities in a window like this.

No, the authors hypothesized that it might not be the eclipse itself, but the stuff surrounding the eclipse that leads to more traffic accidents – more people driving being the number one factor. But more than that, driving while rushing to get somewhere for an event that can not be delayed. And, of course, the inevitable celebrations that go along with the festival-like atmosphere a modern eclipse engenders.

So they used a three day period, centered on the eclipse as their exposure window. For controls, they looked at the same three-day period a week before and a week after the eclipse.

The primary findings are here. As you can see, during the days surrounding the eclipse there was a significant increase in traffic fatalities. On the order of around 30% higher than the control periods. This is similar, in fact, to the increase in traffic fatalities we see around Thanksgiving, Memorial Day, and the 4th of July – all big “driving” holidays.

Examining key subgroups, they found this eclipse effect was stronger when alcohol was involved, and when younger people were driving.

So what do we do about this, with another eclipse imminent? Well – we can remind people that traffic is going to be a bit worse around the 8th – and to give themselves plenty of time to carefully, calmly, and soberly get to the place they want to watch the cosmic ballet unfurl.

And, of course, if you are going to look at the eclipse – look at it through something like this – a solar filter. There aren’t too many ways the eclipse can hurt you directly – but eclipse-related solar retinopathy is one.

A version of this commentary first appeared on Medscape.com.