Taking a walk at 6 p.m. in December or January is apparently the riskiest of times to be a pedestrian.

John Nelson pulled together data to draft up a chart that visualizes “The Horizon of Pedestrian Risk.” As one might expect, the darkening hours of the year are more dangerous times to be a walker.

horizon of pedestrian risk

The “Horizon of Pedestrian Risk” (Image source: John Nelson)

The chart, which Nelson argues is actually a map (more on that later), shows “the proportion of American traffic fatalities that involved pedestrians by time (left-to right is the time of day and night while the up-and-down splits up the months of the year),” the cartographer explained on his blog.

It’s not necessarily the darkest hours of the night, but the twilight hours when walkers need to be especially careful.

“Do you notice how strongly the band of elevated pedestrian risk bows the way it does? That’s because it is especially dangerous to walk at twilight (sun in your face, difficult lighting for object perception, more people walking about, all that),” Nelson wrote. “But twilight is relative depending on the season, so you see the arc of sunset pushing out through summer months and back in for the winter months. All because we live on a round thing flying through space. The nature of that roundness is unintentionally revealed in this data.”

As Nelson put it in an email to TheBlaze, it’s not that surprising that twilight has more pedestrian accidents. What is interesting is how “the data accidentally paints in a rough picture of Earth.” He called it “an accidental map.”

This is also why Nelson describes it as a map and not necessarily just a chart. Here’s a bit more of his explanation:

Amazingly, or not so amazingly to the tougher nuts out there, is that the very roundness of Earth is echoed in the shape of the curve you see in this chart. It’s like what I would expect to see from a rough radio telescope signal of some distant planet, only it’s our planet. And the signal we see is an emergent reflection of our movements on its curved surface. These traffic events happened in the United States. But the curve would be the same for other Northern Hemisphere places, and it would bend the other way for places in the Southern Hemisphere. Because we live on something that is dynamic, data of our lives often reveals the signal of that dynamic process -a roundabout meta image of Earth. That’s a map.

All in all, chart or map, the visualization might have you crossing the street a little more carefully during twilight hours.

Check out larger sizes of the map/chart on Nelson’s Flickr stream.

(H/T: io9)