Always a sad thing to see, tragic of course, makes you feel sick and often is an horrific display of human cruelty, but fortunately, despite the huge numbers killed on roads, the affect on population sizes is usually negligible. What Nathan describes is quite common, I've seen a good number of pythons dead or dying just off the road or sometimes 10-20 metres off it, which had been hit in the middle of the road. Look closely when you see a dead or dying reptile near a road and you might be able to locate the place it was hit (look for blood, guys, etc). I've seen snakes run directly over by cars, two wheels crushing the mid section of the animal, but after the car drives on, the snake appears perfectly fine, for a few minutes, which is enough to move some distance (while no doubt in absolute agony) before dying. Even snakes which have had their heads crushed, or even removed, will writhe about, sometimes for hours (I've seen this happen to a few things including large scrubbies, which is rather gut wrenching).
Not surprisingly, some of the ones which have upset me most have been Water Pythons. I saw a road killed hatchling near Cairns (probably hit without the driver seeing) and a large adult coiled up just off the road, about 100km north of where the ancestors of mine lived. It looked completely fine, I was really excited about seeing what might have been a not too distant relative of mine, although I wondered what it was doing basking at over 50 degrees celcius. It was fairly nastily injured inside, but looked completely fine on the outside (yes, I dissected it, yes, legally). It was still fresh (any more than a day old and it would have stunk). Quite clearly it hadn't been hit where it was, but after its insides were severely squished, the snake had moved to the side of the road, coiled up and then died of internal bleeding.
The ones which upset me most are those I watch happen. I once leaped out of the car to take a Red Bellied Black Snake off a busy road, but the truck behind me squished it. I've seen a few Tiger and Eastern Brown Snakes down in Victoria die from being tyred, but have never seen anyone swerve off the road to hit one. I doubt many red necks would spot them anyway. One thing many of us have thought about is getting road killed snakes and putting them off the road in lifelike poses, along with several tyre popping nails inserted :twisted: still, for all the people who talk about it, I've never heard of it being done, which jokes aside is probably for the best.