I don't think the worst part is people being impatient. It's how stupid people are and how little they pay attention. Years ago I was in an accident where a guy leaving a parking lot turning left just drove right into the side of my truck. Like straight into the side of the box, not icy, not dark nothing just not paying attention at all. A bad driver is always a hazard on the road whether or not they are speeding or driving erratically, sometimes the slowest drivers are the most dangerous. I don't know how many close calls i've had with people doing 20+ under the limit on a clear dry summer day it causes a huge hazard of people trying to get around them and backing up traffic, if you're not comfortable doing within 5 mph of the speed limit and there isn't a reason for it like being a semi, you shouldn't be on that road.
Closest call i've had was a bike coming towards me trying to pass, I don't think he was back in his lane for 2 seconds before we met. I was driving my dump truck pulling my 210 hoe, not sure how anyone can see 90,000 pounds coming towards them at 55 MPH and think "good time to pass". The part that really pissed me off about it is I think a lot of other drivers would have swerved into the ditch or shoulder, potentially writing off the rig, maybe even killing themselves because someone else did something stupid. I didn't budge on the steering wheel, I did let off the accelerator to slow down a bit but that's all i'm doing. If someone is dumb enough to pass and come at me head on in the semi, unless it's a lot bigger truck i'm staying in my lane because it's the safest option.