What is this movie?

I've been trying to figure out the name of this movie I saw when I was a kid. I'm thinking it's an 80's movie or early 90's. I don't remember much, but it had a chick, who probably had premarital sex and she was cut in half, which was pretty cool. The killer I think was slow. Not full on down syndrome slow, but short bus slow. I'm thinking the movie starts out with a couple "fornicating" In the woods or next to some train tracks and then they get killed by slow bus guy. There is also a scene where they go to the carnival. I know this is vague, but I was around 8 years old with ADD and I'm lucky to remember this much. LOL

the funhouse?

If not The Funhouse, then Clownhouse.

Funhouse