Running over a cat: Slow or Fast (to do more damage)?

Factual Questions
1

Ok, this is a completely hypothetical question. No small vicious animals will be harmed as a result of this thread. Feel free to substitute any other small animal you like if the idea of cats being run over disturbs you. For instance, take “cat” to read “small animal shaped ballistics gel similar to the sort used on Mythbusters” if it makes you feel better. Actually if you are a pet lover you might be better off backing out slowly with eyes closed.

Now then. Spotting several flattened felines on the highway the other day, the following question occurred to me: Would running over a cat at a higher rate of speed (70-80mph as an example) do more damage (greater impact), or a very slow speed, say 5mph (maximizing the time the vehicle is physically on top of the animal)? By damage, I’m talking maximum flatness, spread, area covered, etc.

2

I’ve just done experiment with one of my mothers cat just for you.

I’ve taken exhibit A (lets call her Tabby) and tied her down. Well, I didn’t but I’ll guess anyway. The answer is in your heart. Put yourself in that position and which would you think causes more pain? I’d say go as fast as possible but maybe it would be best to go slower and sit on top of me until I die? Then go and reverse and drive over me again, repeat x6. In that fashion, the pain would be less. You could experiment yourself without living things I would assume.

3

I do not have a factual answer to this question, as I suppose it requires some experimental evidence and I do not want to volunteer to collect it.

However, a car impacting a biological object at high speed will probably do a lot of damage before the object goes under a wheel. The object is getting broadsided by a tire moving at 70 before the tire even rolls over it. Once the rolling-pin action begins I would think (but would depend on automotive engineers to tell me for sure) that the car’s suspension will not respond as quickly to a bump as it would if the car were going slowly, and the force on the object will be greater, albeit for an extremely short period of time. My Toyota Sienna has a contact patch of about 8" longitudinal. At 70 MPH it would take about 0.006 seconds for the contact patch to run over a fixed point.

Given that kinetic energy varies as the square of speed, a car doing 70 MPH has nearly 200 times the kinetic energy as one going 5 MPH. So I would say that the faster car is going to cause more overall physical deformation of the object due to offloading some of that energy.

I don’t know what the ability of a biological object is to withstand static vs. dynamic loads, but I’m thinking that the relatively fragile nature (compared to a car) means it won’t make much difference. The faster car is more of a dynamic load (fast onset, short duration) where the slow car is more static (slow onset, long duration). (IIRC from my days at Ford they used to do static-load tests on body parts to see how metal fatigues. We also did these tests digitally using a program called NASTRAN.)

On preview: Hennessy,I don’t think the issue is pain, but rather the question of how much pancakeness that results. I think the cat’s a goner in either case.

4

If you really want a general answer to the question, you could have phrased it much less creepily. Like using possums or skunks or squirrels (which are small animals that get hit far more frequently than cats). And by asking in a more fact-seeking manner which type of impact hurts them more, instead of making it sound like you are seeking advice for the best way to cause maximal pain to the animal.

Bygones at this point… but for future reference.

5

Just for the record, I am a cat lover. I have had three cats over the years that I treasured. And I took no offense at the OP and none appears to be intended. Fair warning was offered in the first paragraph, if the title itself wasn’t enough warning. The question seems quite factual and makes no mention of pain or suffering. Just physical deformation. And all quite hypothetical.

6

In practice, the faster collision is going to do more damage if for no other reason than that it gives the animal less time to get out of the way.

7

When I was a teenager, I witnessed my aunt’s dog getting run over. The dog ran ahead of us, out into the road, when a speeding car hit it. It was bowled over by the initial impact with the car’s bumper and went forward and sideways, rolling along the surface of the road.

I do not think any of the car’s tires actually touched it; it was moving too fast across the road before it get hit, and was quickly out of the path of the car. The damage was done by the one initial bumper impact.

My father buried it in the back yard.

8

From the professional snake killers at Anniston Army Depot: Just running over the snake won’t kill it. You have to time it just right so when you slam on the brakes, you smear the snake’s body into the asphalt. Some of the guys have a near 100% kill ratio.

9

A cat is small enough that a tire could roll over it rather than collide with it. The cat may have to lie flat for that to happen, as opposed to arching up which would yield a collision.

The faster it’s rolled over, the less harm will be done.

10

Yeah, you’re creeping me out, but not enough for me not to post, apparently.

I agree with the posters that say fast tends to knock the cute leetle buggers out of the way–the impact and subsequent fly through the air, then the second impact kills them handily with little muss or fuss.

I came across two cats killed in this way recently, and was immensely grateful that if they had to be dead, at least they weren’t, uh, spread.

11

Yeah I didn’t intend to question how to maximize the pain, but was just wondering in a “dirty jobs - roadkill cleanup” kind of way what would cause the biggest mess. I’m assuming it would die more or less instantly in either case. I am truly sorry if any cat lovers are offended by my analogy.

12

Now how about damage to the car. I hit a cat in my car traveling about 80mph on a freeway interchange at night. I never saw the cat, nor did I know what I hit until I pulled to the side of the road and drove in reverse to the impact area. The cat basically popped outward from every oriface and opening, including ears and eye sockets as a result of the tremendous hydraulic shock. My car needed a wheel alignment as a result of the impact.

If I would have hit the cat at 5mph I would’ve saved the $50 cost of an alignment. So, faster does more damage to your car and your wallet.

13

If the cat were zero-thickness to begin with, then the only factor of concern would be the weight of the vehicle borne by that particular wheel. In that case, minimizing the amount of time during which the wheel’s load is exerted on the paper-thin cat would minimize the amount of damage.

However, a real cat has non-zero thickness. Upon first contact, the wheel has to move upward to get over the cat, which requires upward acceleration of the wheel, and therefore a downward force on the cat that is greater than the weight borne by the wheel. The faster the vehicle speed, the greater the upward acceleration that is required of the wheel.

The proof of this is in driving a car over a curb. You can ease your car’s wheels up to a curb and then briefly nudge the gas to coax the wheels up and over, and everything will be fine. Hit that same curb at 70 MPH, and you’ll likely bend all four rims due to the upward acceleration being required of your wheels (this assumes a curb height less than the maximum upward travel available in your car’s suspension; if the curb height is greater, then you are also likely to bend/break suspension components).

And then of course there is the forward impact of the tire at first contact with the cat, also happening because the cat has non-zero height. Higher speed will do more damage here, too.

14

You know, OP proposed "cats,"which slightly annoyed a down thread reader. Schodinger, were he to have OP’d here, would use constantly the problem of a smeared cat. Is that wose or better than “flattened cat”?

15

I see a suggestion for Mythbusters!

You seem to be negating the possibility of repeat strikes. First strike kills cat, but leaves cat in middle of roadway in line with path of tires. Ergo, lots of cars run over cat, proceeding with pancaking.

That’s the general principle for “sailer” animals found on the road.

16

I can’t believe I’m going on record with this, but … don’t bother calling Mythbusters. I have, quite inadvertantly, done the research myself.

Case 1: my neighbor’s incredibly stupid cat. (I posted about this here.) The cat in question was apparently snoozing directly behind my front left wheel. I got in, started the engine, waved good-bye to Mr. Horseshoe, put down the e-brake, went to shift, saw my purse strap had looped over the gearshift, moved my purse, blew Mr. Horseshoe a kiss (yeah, I’m goopy like that), shifted into reverse and THEN started to roll. That cat had a good ten seconds after I started my car to wake the hell up. He did not. bump Something shot, squalling, away from my car. One horrified glance at the Other Shoe’s horrified face told me everything I needed to know.

Chase ensued. A hose had to be involved when he hid in some dense shrubbery. Frankly, in hidsight I should have been able to tell he was probably going to be OK just by how hard it was to catch him. Vet trip ensued. Cat stayed overnight for observation, to make sure all internal workings were Ok. (Read: he peed and pooped successfully.)

result: No broken bones, no internal injuries, no ruptures, just a bruised leg and a weeklong limp. Vet tech assured me it happens often.
Case 2: This happened just the other week: going home in the dark on a 3-lane road near a wooded area. Car next to me is doing that annoying thing where you speed up to pass them and they start going faster, so you drop your speed and they start slowing down. (Don’t think he was playing games; fairly certain he was on his cell phone.) I look in my rearview to see the headlights of a car that is bearing down on us rather fast. In a few seconds, he’d come up on us and swerve over all three lanes to zoom around us both - he was going that fast. Picture a cop on his way to a robbery, except, y’know, not a cop. (Both of these are, unfortunately, common driving behaviors in Dallas.) My eyes go from my rearview back to the road, I just have time to think “Well, he’s just gonna have to go around” when a medium-sized raccon came barreling out from the shrubbery into the road directly in front of my car. There was literally nothing I could do without directly causing an accident. In fact, if I’d somehow missed him one of the other two would have hit the raccoon, so either way he was a goner.

result: raccoon dropped like a stone. I felt really, really bad :frowning: but dammit, there really wasn’t anything I could have done.

So in conclusion - since a medium sized raccoon is roughly the same size as a well-fed housecat (you shoulda seen the gut on this thing) - I can tell you that in a lightweight compact car, slowly rolling over an animal is not necessarily going to hurt it much, but bashing into it at 45 mph will, for sure.

17

We would do something similar, the difference being, we would utilize the emergency brake. It seemed to make it a little harder to time just right, (seeing as how you only had one tire to do the job!) And you’re correct… If you just rolled over a snake, without “sliding” a tire across 'em, you usually observed them crawling off the road, in the rear view mirror. Yes, I know it makes me sound cruel and even inhuman, to some. But take my word for it, I no longer do a*** LOT*** of the things that I did as a pre-teen/teenager.

18

What about with a small animal such as a human baby? Would the answer be the same?

19

In terms of the analysis of what the car is doing, pretty much the same, although the parameters of a baby are a little different than a cat, being closer to a spherical shape and possibly having a more robust skeleton. But I’m not an anatomist.

Somewhere in there, there is a dead-baby joke that we thought was so hilarious when we were 13…

20

Several time Road-Kill Ace (34 confirmed kills) checking in, here. To confirm the kill, you have to go back to check that it’s dead. I only had to finish off 1 seagull. They don’t generally flatten. That takes several cars going over the dead body, regardless of speed. Them bodies are tough. The life within them, not so much.

And no, the only pets in there (2 cats), I didn’t inform the owners, because they both were in the middle of nowhere, so which house several hundred yards down the road do you go to, at 3 AM (waking up the possible, but probably not, owners), when you have a jobsite to get to that you have to get to on-time, at 5:30 AM, and still have 2 and a half hours to drive to get there? Sorry, I have a living to make. Don’t let your cats run loose, and you won’t have that problem. I owe you zero consideration. The cat, on the other hand, I at least owe the courtesy to go back and put it out of it’s misery.

ETA: Fortunately, I never had to do a cat. I like cats. I have 3. They don’t get to run loose.