

Wednesday, January 7, 2015

Just How Many More Car Crashes Are There in LA When it Rains?


By Bianca Barragan, January 6, 2015

If it's raining outside, Los Angeles drivers know to leave earlier for work and to expect to see some appalling driving on the road. Is it really any worse than usual though? Yes! Data from 11 years of reports from the National Oceanic and Atmospheric Administration, plus numbers on car crashes from California's Statewide Integrated Traffic Records System suggest that more accidents do happen when it's rainy (duh). The visualization below (via CityLab) shows that dry weather crashes (red lines) usually top out around 10 per hour, even during rush hour. But rainy weather crashes (blue lines) far surpass those numbers, coming close to 15 crashes in the three o'clock hour. Yikes!

rain crashes.jpg
[Image by Noah Deneau via CityLab]

Popular explanations from Reddit, where the graphic was first posted, as summarized by CityLab, include: "Californians tailgate too much; they're so used to drought they've forgotten how to drive in rain; [and] the state's arid weather causes copious build-ups of roadway oil, creating slippery, hazardous surfaces when the drops start falling." Those are all logical-sounding and may even be true, but there isn't a chart yet for cities that are famously soaked, like Seattle or Portland, or even a sort of middle ground city (any place not in the middle of a megadrought would do) to compare LA's increased crash rate to.

The chart was also made with the assumption that there are the same amount of cars on the road in wet weather as there are in dry weather. But it's possible that there are more cars on the road in the rain, as people who otherwise would have walked, biked, or taken public transit decide to drive instead. The guy who made the graphic has been contacted by an employee of the NOAA who said that the organization is working on rolling out a similar analysis of the relationship between rain and traffic collisions, so there's still a chance this LA stereotype can be put to rest (or definitively confirmed).

· Proof that California's Drivers Can't Handle the Rain [CityLab]