Usually when a person hears the term rubbernecking they do not think about fiction. What comes to mind is a car accident. Maybe you're thinking police on the side of the road, cars smashed up, and an ambulance at the scene? There is that definition, but there is another way to use the term.
Wikipedia says, "The word rubbernecking has also come to be used more generally to describe voyeuristic interest in someone else's business or difficulties."
So how can you use this in your novel to set you apart? Simple. Just make sure you add in those things that people can't seem to turn away from. It's like adding a bit of gossip to spice up your novel.
Have you ever started a story with, "Oh, man I just heard the most disturbing thing on the news."?
Or, "The strangest thing happened the other day." People love the interesting, sometimes sick, things that they hear that are not your everyday gossip.
And it's not just gross things either. It's amazing love stories, stories about psychic moments, or miraculous rescues. People love to hear things that are different from the norm.
I know what you're thinking. You're thinking that your story is out of the norm, but that's not what rubbernecking is. Rubbernecking is all the strange stuff you see or hear on your way through your story. Your story should be fantastic and interesting in it's own right, but give the readers a little something extra.
Make the reader slow down in places because you've just given them something to gawk at. There are all sorts of opportunities for minor characters to have a big impact. Maybe your main character see's the neighbor taking out the trash and she wonders how she's doing now that she's out of jail for killing her newborn. Or maybe it's a supporting character that has half of his body scarred from burns.
On a lighter note it could just be a few racy sex scene's (depending on what you're writing of course).
These things shouldn't take away from the story, they should add to it. If you're main character has hidden pain from the past (and most of them do) maybe the short description of the man with scars all over his body is a metaphor for your main character's inner pain.
It should be subtle of course, and short. Rubbernecking is not a subplot or worse, an entirely different story. It's just a little extra kick to the details of your book.
The reason for doing this is, of course, to make your novel more interesting. Why not just say use every opportunity to make your novel more interesting to your reader? Well, you could say that, but I like "give your readers an opportunity for rubbernecking" better!