Timid or panicky drivers. I was behind one this morning, and I would swear she stepped on her brake pedal at least once every 5 seconds, with no cars in front of her, plenty of space behind her, and on a straight road.
That would make me nuts too. I rode with someone years ago, only a couple years older than me who would at times drive 20 miles below the speed limit when there was no good reason to and it was truly unsafe to be going that slowly but she refused to even go the speed limit. If you're that timid about driving, you shouldn't be.
Hehe - a couple of months back i went outlet shopping with a couple friends from work. One woman drove, and it was a straight shot up the interstate. But she drove well under the speed limit, and wouldn't pass a truck going even slower than she was, even though the rest of the road was WIDE open. at the end of the day, she wanted to hit one mroe store, and my other friend and I waited in the car. we both agreed that she was never driving us again!
I scare people the other way. I grew up and learned to drive in Miami, FL. The traffic here is awful. Sometimes I think other drivers try to run you off the road for fun. I try not to be aggressive, but there are times when I have to be. I have a fair amount of family in the Atlanta area, and those people's crazy comes out in the form of fast driving, so I had to learn how to operate at higher speeds just to keep from getting run over.
Then I moved to North Dakota. I had to drive into Minneapolis quite frequently, and I'd often times have a friend with me. Now, for somebody from ND, Minneapolis has really heavy traffic. To somebody from Miami, LA, or NYC, the traffic in Minneapolis is a mere annoyance*. Apparently, my definition of "normal" city driving scared the beegeezus out of several of my friends, who considered my driving aggressive. I'd really hate to see how they'd react to driving in a city that actually has bad traffic.
*The traffic in Minneapolis does get congested, but people are, as a general rule, polite and non-aggressive. If you turn on your turn signals, people will actually let you in as opposed to cutting you off, like they do in Miami. They also tend to be polite and reasonable when it comes to allowing people to merge or turn out of a shopping center. These things make driving there so much more pleasant.