Why is such a high percentage of roadkill on the right shoulder?

Factual Questions
1

Okay, DeathLlama and I just got back from a trip to southern Ohio to visit relatives. As they live far from the airport, there was a lot of driving over very flat land. We noticed immediately that there was a lot more roadkill than we typically see in SoCal, and after a few days, it became a game to keep a tally.

We saw 106 dead things on the 52 to Lexington (had to go to the Kentucky Horse Park, of course), counting east-bound and west-bound trips. Of those 106, 6 were in the center of the road, 5 were on the left shoulder, and 95 were on the right shoulder.

In my fam’s local area, we counted 12 dead things between grandma #1 and grandma #2. All of them were on the right shoulder.

Then, driving to the Columbus airport yesterday, we counted 93 dead things. About 8 were on the left shoulder, 6 in the center of the road, and all of the remaining ones were on the right shoulder.

My question is…why? Surely not all of the animals were struck in the right lane and sent sailing to the shoulder? Some of them looked to be too mangled to have limped there themselves, and some even had (yeesh) blood stains in the road that showed them more or less being dragged to the right.

I postulated that the highway patrol might’ve moved the animals to the shoulder to remove them from driver’s paths, but DeathLlama thought that unlikely–it seemed to be a rather time-consuming menial task. He thought that basically an animal is more likely to be hit in the right lane, and that all of the hit animals either drag themselves that far or are thrown that far. The ones hit in the center of the road are so flattened so quickly that they aren’t as visible, he says.

That seems unlikely to me as well, but hey. I’ve been wondering all during my vacation–so, is there a Doper to elucidate us? Why is this so skewed to the right?

BTW…we saw mostly dead squirrels, opossums, and raccoons, but also had a fair share of cats, a few dogs, a large groundhog, and what appeared to be a small deer.

Mmm…dead things.

2

Come to Wisconsin right now and head out on the highway. With Chronic Wasting Disease we have right now and the free for all on killing deer. (Officials want ALL deer killed in certain areas regardless of age, gender etc). So I don’t know if its the disease killing them or the hunters driving them out of the forrest or a combonation of both, but there’s alot of dead ones on the highways right now (in fact some of them are even making it into busy downtowns of citys).

I do have a question for you though. What type of highways are you driving down. Is this a divided highway with a raised median or cement wall, or a divided highway with just a line down the center? Or is it a more or less one way highway with gravel on both sides and the “oncoming” traffic seperated by a large distance (for example on the other side of a freeway or river or a forrest/ thick brush)?
Basically what does an animal need to do to get safely across the road? Does it have to go though two different directions of traffic or just one? Am I making sense?
Basically

3

Yes, you’re making sense. For the majority of the time, we were travelling on 4-lane highways (2 going one direction, 2 the other). The lanes were separated by a v-shaped grass-covered median. There were sections where there was an actual wall in the median, but that was the exception.

The animals would need to skit across 2 south/eastbound lanes, through the grass, and then across the 2 north/westbound lanes to reach safety.

4

So here’s my theory then…

Anything dead on the left shoulder (or the inside)–Animals who made it through the first two lanes of traffic…almost, got hit by an inside car and flung to the inside OR Animals who made it to the inside and got hit as the were heading for the second part.

Anything dead on the right shoulder (or outside)–Animals who made it through the first two lanes and almost throught second two, getting hit by an outside car and flung to right shoulder OR animals who got hit as soon as they started in.

So I believe your answer would be that there is a higher percentage of roadkill on the right side because there is a higher percentage or animals who attempt to cross the road then who actually make it.

5

Or to restate that if all animals have an equal (but unlikely) chance of crossing any highway at any given time (regardless of “expierence”) then you have lot’s of animals on the outside and only a few on the inside.
Say for every 10 animals, 1 succesfully crosses. If 100 approach the road, 10 end up in the middle (alive) and 90 dead on the side of the road. Of those 10, one will make it through the second part of the road and 9 will die trying. With these crude numbers out of 100 animals we have 90 on the right shoulder, 9 on the left shoulder and 1 that made it all the way.

6

Because most animals are right handed they tend to stick to the right side of the road.
In all seriousness I believe the statistical example Joey P makes is probably most in line with reality.

7

Could it be that roadkill struck by a right front tire will have the propensity to go right? Then, only animals struck in the dead center of the road are allowed the chance to play roadkill ping-pong between the front left tires of opposing traffic.

Another theory that I witnessed, was a dolt in a small sedan, middle of a cloudless sunny day, ran right over a dead deer. right. directly. over. He pulled off to the right as his little four cylinder engine struggled to keep moving forward with the added friction of a road-smearing carcass. I hope he paid for his inattentiveness with an unpleasent procedure of jacking the car up and dragging said smear out from under his car. I sure didn’t stop to help. I figured it was a lesson he needed to learn.

8

My curiosity then, JoeyP, is why the animals aren’t, say, on the edge of the road, or maybe a foot inside the right lane–would nearly all of them be flung to the shoulder? Very few of them actually wind up on the road itself–if hit on the right side of the road, why not wind up on the road’s right side–rather than shoulder?

9

That’s yer clue … This is an well-known statistical phenomenon. Basically, wherever on the road the animal (or debris of other kinds) ends up, there it stays. Until another car comes along. If the animal is in the road, it may get hit again (or very nearly hit), which tends to move it around somewhere. But if the animal is on the shoulder, it generally doesn’t get hit again. Over time, any animal ends up on the shoulder. Not because it has any general propensity to move in that direction, but because that’s the one stable location in the near vicinity.

10

In addition to the theories already up above (animals approaching road and the state patrol moving the animals) there is also the factor that roads are built to have the apex in the middle (or furthers part of the left lane) so precipitation drains more efficiently. I’m thinking this helps drain the carcasses to the shoulder (right side) of the road.

11

There’s also the chance that a fair number of creatures start to cross the road, sense a car coming, realize they’ve made a big mistake, and try heading back to the shoulder just a bit too late. This would considerably increase the number of critters getting hit towards the righthand side of the road.

12

Plus my guess is that more cars are driving in the right lanes, therefore more collisions with animals happen in the right lane.