The aftermath of a multi-car pile-up on Florida's I-4 in 2008. Reinhold Matay/AP

Why are Southern interstates so deadly? It could be a lethal mix of high speeds, distracted driving, and lax regulations.

Driving in America is becoming more deadly, with nearly 18,000 people killed in traffic incidents in just the first six months of 2016. That represents an increase of more than 10 percent over the same time last year—a period that saw similar gains over 2014. Fatalities per 100,000 miles driven are at a 7-year high. The troubling death spike may have several causes, including the fact that more Americans are driving more as the economy has recovered. But it’s believed that one big culprit is distracted driving. As CityLab reported earlier this year, American drivers are texting, talking, futzing with with vehicle’s ever-more-complex entertainment systems, and otherwise ignoring the road more than half the time they’re behind the wheel. The epidemic of distracted driving is thought to be responsible for about 9 percent of all road fatalities. Meanwhile, anti-cellphone traffic laws remain frustratingly difficult to enforce in most states, and nonexistent in a handful of others.

Under the mantle of a policy platform known as “Vision Zero,” a growing number of cities have launched campaigns to limit and eventually end all road fatalities, and the U.S. Department of Transportation recently jumped on bandwagon, too: The “Road to Zero” coalition will fund initiatives to improve traffic engineering, law enforcement, and educational strategies across the country. It’s all aimed at getting state laws aligned with the best road safety practices out there.

The risks of distracted driving in this under-regulated terrain are suggested by a new analysis that Seth Birnbaum, CEO of the auto insurance marketplace EverQuote, put together. Their safe-driving app EverDrive (co-developed by Cambridge Mobile Telematics), which captures a driver’s phone use while their car is in motion, has yielded data from 6 million trips over 75 million miles from 38,000 registered users nationwide. Between this phone-use data and their analysis of crash statistics collected between 2010 and 2015 by the Federal Highway Administration, the company put together a ranking of the nation’s most lethal highways. The results show how risky driving habits, coupled with an absence of state policy attempting to curb it, may be pushing up fatalities.

Bad roads: The 10 interstates with the most per-mile fatality rates are I-4, I-45, I-17, I-30, I-95, I-19, I-10, I-37, I-26 and I-97. (EverQuote/Google Maps)

Many of the interstates with the most fatalities per mile are, unsurprisingly, some of the most heavily traveled in the nation. Florida’s infamous pileup-magnet I-4, which runs from Tampa to Daytona Beach, tops the list. The southernmost cross-country highway, I-10 from California to Florida, is up there, too, as is densely trafficked I-95 from Maine to (again!), Florida. Seeing the list in its entirety in the map above really emphasizes its southern bias. One of these highways is located entirely within the state of Texas (I-45) and three more pass through the Longhorn state (I-10, I-30, I-37). Arizona also has three of the top 10 dangerous interstates running through it.

Why would such relatively dry, temperate and ice-free highways be so dangerous? Sheer volume is part of the answer: All of these are extremely well-trodden roads, with traffic volumes on most of them topping a quarter-million cars every day. But these states also clock in high on various rankings of distracted driving, with Arizona and Texas two of only a few states with no kind of behind-the-wheel ban on technology use (Montana is another). Texas also enjoys a new rural toll road with a posted 85 mile-per-hour speed limit, giving drivers there the highest average speed limits in the nation. Cell phone motion data from EverDrive supports the theory that drivers in at least two of these states are picking up their devices more than in others: Texan users turn to their phones an average 1.35 times per car trip and Floridians 1.4 times per trip, compared to a national average of 1.1 times.

Bear in mind, of course, that these numbers are based on behavior from just a small fraction of the country’s drivers. And interstate highway travel is only one context in which to consider dangerous driving. Statistically speaking, the nation’s scariest byways are in farther-flung locales. Some 50 percent of traffic fatalities occur on rural roads, according to the FHWA, despite just 15 percent of the population living in rural places, as designated by the Census. Compared to interstates, rural roads are often curvier, narrower, undivided, less consistently paved, and poorly lit and marked. Medical attention can also be farther away.

The FHWA’s datasets for rural versus urban road fatalities aren’t available yet for 2015, so it’s not yet clear whether distracted driving is also exacerbating traffic deaths in rural areas. No doubt, as federal officials scramble to stem the tide of fatalities with enforcement and education programs, the changing contours of this bloody geography will be revealed.

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