When the sun dips into the horizon during Wyoming's twilight hours, dangers are suddenly everywhere. In an instant, dark figures begin darting onto the state’s roads, and the sound of squeaking brakes can be heard from Rock Springs to Cody. We call this time of day "deer o'clock," and we grip the steering wheel just a little bit tighter. Some of us even slow down.

Driving during a light-fading Wyoming evening is a test of mental alertness and reflex response. In a state where deer and antelope outnumber humans, the odds are stacked against you when it comes to having an unexpected encounter with a jay-walking animal. In 2002, the Wyoming Department of Transportation reported 1,681 vehicle collisions with wildlife, which they say under-represents the number of animal carcasses they find on Wyoming's roads.

These collisions are scary and sad. I don’t think I’m alone in knowing someone who’s been killed in one. Not long ago, while driving along Highway 191 near Pinedale, I slammed on my brakes for a small herd of pronghorn antelope nervously scooting across the highway. As the car skidded closer and closer, I locked eyes with the lead antelope in the pack. We were both terrified. I managed to come to a halt inches from the cluster of animals.

Only a few minutes later, just as I was catching my breath, I passed an antelope that hadn't been so lucky. She’d been hit by an oncoming car and was struggling by the side of the road, her legs thrashing in the air and twisted at an unnatural angle.

It's not easy to be a twilight driver in Wyoming, yet it's far harder for wildlife. At less than 500,000 people, the state isn’t densely populated, but the open range of a couple of hundred years ago is mostly gone. Today, oil and gas rigs that make daily stops at wells and roads, private land development and rampant fencing have all created an obstacle course for migrating wildlife, especially along Highway 191 in southwestern Wyoming. And it will only get more congested, because more than 90 percent of southwest Wyoming's public land is available for oil and gas leasing and development. You can see the future in the thousands of gas wells that already spider out in a giant web of service roads, powerlines and pipelines.

This development is starting to choke the largest big-game migration in the Lower 48 states, which happens right across Highway 191 each year. Nearly 50,000 pronghorn antelope migrate through a natural funnel from summer ranges in Grand Teton National Park to winter ranges farther south near Pinedale. Everything converges at a bottleneck named Trapper’s Point. This narrow corridor is the most notorious wildlife crossing in Wyoming. But today, instead of the fur trappers who rendezvoused here in the 1880s, vehicles zoom 70 miles per hour along Highway 191.

Wild animals have to scramble for their lives to escape oncoming trucks and cars, and many vehicles careen off the road to avoid a collision. Who's at fault? You can't blame wildlife; they're following migration instincts thousands of years in the making. But they're running against a nation on the move.

Nearly 4 million miles of roads and 200 million vehicles zigzag across our great land. According to the nonprofit Defenders of Wildlife, hundreds of thousands of animals — large and small —are killed on our highways every day.

So what's the twilight driver to do? One thing we can do is be more active in how and where our roads are built. For most of us, the only time we think about transportation planning is when we're stopped for a road construction project. But each year, new roads are built and many existing roads are widened in the United States. There have been studies to find ways to keep wildlife off the roads, such as installing flashing lights and over-and-under passes that give wildlife crossing alternatives. As taxpayers, we need to speak out so this research continues and proper planning can dictate how our roads are built.

Wildlife advocates don't need to oppose every new road or road-expansion project — after all, we all drive cars. But as development continues to choke the West, wildlife shouldn't always have to take a back seat when it comes to road planning. Both humans and animals deserve a home on the range where we can travel safely.

Kerry Brophy is a contributor to Writers on the Range, a service of High Country News (hcn.org). She is publications manager for the National Outdoor Leadership School in Lander, Wyoming.