I will never understand why people will ride your bumper on a 4 lane road when you're obviously going under the speed limit. I also don't understand why they will ride right beside you, all they are doing is taking away an escape and making one more thing to try to avoid in an emergency avoidance maneuver. I had a guy run up on me while I as driving my work truck (Kenworth T300) down US 40, he had to be running better than 65 to catch up to me as quick as he did, then slowed down and drove right behind the cab where it's hard to see them for at least 15 miles before he turned of. I slowed down, I accelerated, he'd just adjust his speed and stay right next to me. Really really annoying!i was on 20 bypass around south bend, i had sand in the back of my truck and could hear it hitting my rear window going 60 in a 65 so people could get around me, had this stupid person come flying up behind me and ride my bumper there was no one with in 1/4 mile of us so i let off the gas and let it slow down to 35 mph before they pass me, then they just kinda set be side me as i get back to 60. i drove semi for 2 yrs so ive seen a few things in my travels