In order for them to be found on the SIDE of the road, we’d have to postulate drivers actually swerving out of the safe flow of traffic to deliberately run them over.
Pepe Le Pew is just too lovable for that to be a plausible postulate.
Or:
- injured animals staggering a final few feet before expiring
- animals being killed by a sideswipe, rather than a direct hit
My bike got, um, contaminated. I don’t think I got any liquid on me, though my clothing may have adsorbed some of the scent coming off of the bike. I was enroute to a club breakfast when it happened (a couple of miles from my destination), and a number of other riders came in via the same route. They all saw the dead skunk in the road, and when they walked past my bike in the parking lot at the restaurant, they instantly knew I was the one who had hit it.
I had to wash my bike a couple of times before the odor was mostly gone.
More to the point - no-one in their right minds wants to hit a skunk, and have that smell on their car. 
Great horned owls and black vultures have poorly-developed senses of smell. They’ll happily feast on a meal of skunk’s ass. The black vultures are particularly plentiful in the Austin area, and those mofos are huge.
This is pretty close to the “factual” answer. Saw it on a skunk documentary. They are somewhat fearless of predators and ignorant of Subarus.
BORING! 
Then there is a shitload more skunks than I thought were in Wood Dale. Which is possible, but it doesn’t make “confirmation bias” any less boring. (another ;))
Massengill douche kills skunk whiff dead. Yeah, it sounds like a joke in bad taste but my dog got sprayed (translation error: dogs get down on their elbows and raise their tails to say they want to play while skunks get down on their elbows and raise their tails as a warning before they spray) and the stench wafted off her in a fine mist wherever I squirted the Massengill. Off brands did not work as well.
You saw many skunks this year. You saw fewer last year. Random chance, Dude.
I drive that way every day and they all died the same night. Plus I grew up in rabies country so I am (over-)sensitive to weird animal behavior.
Those of you who have not had experience living where there were occasional rabies outbreaks can see something similar in The Zombie Survival Guide’s Class One outbreak, except with sick animals instead of zombies. And you shoot the body, not the head. The head goes to the county health department. Well, it did back then. They probably have better tests now.
Knew someone who got a fine hunting dog that was a stray in a “shoot all strays on sight” area. Kept it isolated for a while until he was sure it was healthy, though.
It’s Autumn and many regions experience warm days followed by frigid nights. Perhaps the skunks are lured into the road at night by the ambient heat radiating from the pavement.
Then this would be a more common experience because Autumn comes along every year and lasts for more than one day. Lasciel is right in that most things consider skunks inedible, and budget problems may cause the local authorities to not pick up the battered corpses (some are now gone but others are turning into oily spots with black and white fur), but that would explain an accumulation of skunk stiffs, not a sudden spike.
Yeah, I know it’s probably a fluke, but it’s fun to think about possible causes. And I love worst-case scenarios, as well as realizing that Max Brooks could have as easily been writing about rabies as the zombie virus.
In Nor Cal, I call Jan/Feb, dead skunk in the road season. Dead skunk every couple of miles on a country road. My theory is that they are in the middle of mating season and have no fear of cars as they have no predators. Thunk.
Obviously a get-together of station wagon owners not far away…
Can’t you just make a skunk-friendly bridge or tunnel for them and avoid all the messy aftermath?
Q: Why did the chicken cross the road?
A: To show the skunks that it can be done.
Feel free to replace skunks with the most common roadkill in your area- 'round here, they be armadillos.