Imagine you're on your way home from a great day enjoying every last minute of daylight in the great outdoors. You've been hiking, foraging, scouting, fishing, and you ran out of water an hour or two ago, so you're a little tired and delirious. The visibility is low as the sun begins to set. You have to turn on your headlights and maybe even squint to see where you're going.
Slow down during the twilight hours. It's summer. You're not the only one that's thirsty and tired. Animals are moving long distances in search of grass that's still green and water sources that haven't dried up yet. Maybe they're even being pushed away from their stomping grounds due to forest fires. Either way, the end of the day at the end of summer creates a lot of roadkill, and as a hunter, it's heartbreaking to see how many animals meet their maker just before the season opens, and rot on the side of the highway. Nobody's putting up crosses or stuffed animals on the side of the road to remind motorists that an automobile accident took a life in this curve or over that hill. There's simply buzzards and bones when it's already too late and it happens again.
I don't have a lot of faith in those whistle gadgets that fix to the bumper. If I had been stumbling around all day on a full stomach of fermented apples and pot leaves while looking for a drink of water, I'd probably freeze in my tracks if you shined your brights at me in the middle of the road too. As drivers, it's best to take responsibility for maintaining a rate of speed where we can not only spot wildlife, but avoid it or stop if it decides to move into our path.
With that being said, something most people don't think about when approaching deer in a vehicle is that if you're going slow enough to stop and take pictures of it, you're also teaching that animal a learned behavior, giving it a false sense of security that vehicles aren't a threat. I know I've done it more times than I could ever count, pull over, fumble around for the phone and try to get a quick snapshot of the animal in it's majestic element of wilderness. I've gotten a few really good shots doing this, but more often I find myself seeing deer that don't bother moving as I approach them with my vehicle. This spring, I saw 3 yearlings wandering in a ditch that were darting back and fourth into the road for nearly a hundred yards as I passed by. I turned to my passenger and said, "These dumb kids are going to get run over, they need to quit playing in the street!" That's when I rolled down his window and yelled across the cab of the truck, "WHERE ARE YOUR PARENTS?" Only a few seconds later, a startled doe seemed to appear out of nowhere and herded her children back into the forest and out of the road.
Deer need to fear vehicles, not feel like they're posing for your instagram muching on ryegrass and crabapples. The best way to do that is yell or honk the horn a few times. Be assertive with these traffic obstructions, their lives might depend on it.
https://www.dfw.state.or.us/resources/hunting/roadkill%20_regulations.asp