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No one who live here needs this study to know that there are more accidents on freeways and streets during rain events in Los Angeles. Duh. Even so, an electrical engineer and "visualization enthusiast" in Austin merged 11 years of NOAA weather reports and accident data from California's Statewide Integrated Traffic Records System to create a graphic showing just that. Noah Deneau's data set is flawed for what he wants to show, but what the heck, it's a kind of interesting exercise. He says someone from NOAA contacted him and said they are doing a similar analysis nationally. From The Atlantic CityLab:
Fair-weather crash rates peak at 10 an hour for three hours in the early rush, but stay much lower through the rest of the day, according to Deneau's accounting. Meanwhile, accidents during rainy periods soar above 10 for more than half the day, approaching 15 per hour around 3 p.m. As for why this happens, take your pick from the following theories on Reddit: Californians tailgate too much; they're so used to drought they've forgotten how to drive in rain; the state's arid weather causes copious build-ups of roadway oil, creating slippery, hazardous surfaces when the drops start falling.
While the rain-wreck correlation seems clear, there are a couple of limitations to this analysis. One, the rain reports are sourced from local weather stations and not accident sites, meaning that some "wet" crashes might've occurred in dry weather. "L.A. covers a big area split by mountains," says Deneau, "and it's highly possible it's raining at the station in downtown but sunny in Van Nuys, for example."It also doesn't take into account how traffic might swell during showers and storms. "I was mainly trying to show how there are more wrecks during rain," Deneau says. "If you assume for any given hour of the day, roughly the same number of cars are on the road no matter if it's raining or dry, this chart is valid. (Whether that's a safe assumption to make I don't know.)"
