I can never imagine myself riding on highways. I just would like to see the statistics to confirm that my concern is justified.
Riding on highways seems to me not much unlike parachuting or similarly high-risk adventures
(sorry, some people have no choice when the highways are the only roads they could ride on, which is a different thing).
(Actually even if I want to ride on the highways, I'm not qualified since my speed will not pick up.
)
I can assure you that highway riding isn't particularly dangerous. There's a large group of people called "professional bike racers" who ride them all the time. Some die occasionally, but it's unusual.
In your area there are probably amateur riders who ride highways as well. Riding most of the things people call a "highway" on a bicycle is not an adrenaline sport like sky diving. It's not characterized by near death experiences that send your adrenaline up. It's often quite serene.
As others have said, you need to define highway. You may picture on thing they wouldn't ride while they picture something else that you would consider safe. I think you'll find riders who ride highways tend to prefer the safer ones. I know that when I ride highways I strongly prefer quieter ones. I still have to ride some busier highways, some with shoulders (and they're usually very busy), some without (not so busy, but you're getting passed every minute or two) to get to the nice ones.
Highways around here are generally:
* Paved
* 2 lane, or 4 lane divided with wide shoulders
* Moderately trafficked
* 55-65mph
* rural
We also have lots of gravel roads. Some people call these highways (I really don't). They're generally:
* Gravel or dirt
* about as wide as a side street
* very lightly trafficked