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Along the Route 80 roadside in Pennsylvania, carcasses litter the pavement. You get used to the mounds of fur, blood, and bone – as common as road signs. Deer. Porcupine. Deer. Fox. Raccoon. Deer. Was that a bear? I don’t often drive in Pennsylvania, but the amount of mangled flesh there this fall disturbed me. Road-kill numbers had to be up, I thought. Or maybe Western PA is just a road-kill mecca. Which states see the most animal-vehicle collisions (AVCs) and why, I wondered, besides the obvious reasons, of having more vehicle traffic and higher wildlife numbers? And wasn’t all this violent interaction between humans and vehicles a little dangerous?

After some fact checking, I saw my observations in Pennsylvania both rejected and confirmed. Based on claims data, State Farm Insurance reports that deer-vehicle collisions (which account for about 77 % of total AVCs) have been dropping in the U.S. since 2009. But a few states still show surprisingly high numbers of collisions. Pennsylvania tops the list in terms of the raw number of deer-vehicle collisions (101,299 in 2011). Michigan, which sees over 80,000 deer-collisions per year, is second. West Virginia tops the list in terms of per capita collisions. A licensed West Virginia driver faces a 1 in 53 likelihood of collision with a deer in the next year. Iowa, where drivers face a likelihood of 1 in 77, is second. Both State Farm and the Insurance Institute for Highway Safety estimate that about 1.5 million deer-vehicle crashes occur every year, causing over $1 billion in car damages. Yearly animal crashes cause about 150 to 200 human deaths and 10,000 injuries.

All this data on animal and human carnage suggests that deer could be the most threatening animal to human lives. Compared to a handful of shark-attacks and bear maulings, deer-collisions wreak more widespread havoc. Yet while we take precautions to protect civilians from sharks and bears (ie. closing beaches or shooting bears that wander into neighborhoods), we do comparatively little to protect humans from slamming their cars into cute white-tailed does.

November sees more deer collisions than any other month. (From the Dept. of Transportation)

On a positive note, State Farm suggests that in eight of the top 10 states, the rate of deer-vehicle collisions per driver went down from 2010 to 2011. What accounts for the success of avoiding collisions? The national trend of people driving less serves as one simple explanation. Liberal or experimental state culling laws could also help limit deer densities and related accidents. But there is another basic explanation. The states that saw significant decreases in collisions over the past few years are the ones that spent money to provide corridors for animals to safely cross highway systems. New Jersey, Florida, Virginia, Vermont and Montana – for example – all spent aggressively to install underpasses, overpasses, fencing, or throughways designed to channel wildlife to safe passage. And all these states have all seen decreases in the likelihood of collisions.

States that have done little to address the problem, like Pennsylvania and Idaho, have seen collisions flat-line or, in Idaho’s case, increase. A recent report by the Spokesman Review suggests the effectiveness of applying infrastructure changes to highway systems.

Quoted in the article, Kelly McAllister, a Wildlife biologist with the Washington State Department of Transportation, says: “There is definitely an increased awareness all around the country that these kinds of structures are effective. They’re used by wildlife. They do reduce collisions, particularly when you combine it with good-quality barrier fencing, and in the long run, they pay for themselves, really, in terms of reduced property damage from collisions.”

Debate surrounds less costly solutions to the problem, like car-mounted deer-whistles and posting wildlife crossing signs in strategic locations. Deer whistles, which produce ultrasonic noise (16 to 20 kHz) when a vehicle exceeds about 30 mph, have not shown consistent results. The same can be said for wildlife crossing signs. A 2011 USA Today story sites a University of Alberta study that suggests that targeted road signs reduce collisions by 34 %. But other studies refute the logic that sign postings affect driver behavior enough to limit collisions. A University of Michigan study by John Sullivan (2009), for example, suggests that wildlife crossing sign postings have little effect on the rate of collisions. Sullivan suggests that driver speed (and posted speed limit) is a much better determiner of AVCs. This study concludes that decreasing speeds and better car lighting systems could reduce the risk of AVCs. Most drivers, however, don’t favor decreasing highway speed limits. And car manufacturers have little incentive to improve lighting systems beyond current technology.

Public awareness of the issue can help drivers avoid costly collisions. Drivers that know where and when to look for wildlife crossings will be more prepared to react, to decrease speeds appropriately or (according to a State Farm suggestion) to refrain from swerving so as to avoid further risk of injury. But public awareness cannot prevent animals from crossing buzzing highways systems or from making erratic decisions and movements, as excited bucks have been known to do in the midst of their fall mating season (October and November). More comprehensive solutions at state and federal levels require more comprehensive mapping of the problem areas and targeted infrastructure changes to our highway and road systems.

AVCs could be a bigger problem than Insurance industries tell us. Fixing numbers to AVCs is notoriously difficult because a significant number of them go unreported. Many of us tend to dismiss road-kills and animal collisions as a sort of natural hazard of driving. But they don’t have to be so common. Better addressing them with infrastructure would save human lives, animal lives, and a lot of damages.

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