Mud flap Cloyce

An old friend of the old man's, I'll call him Cloyce just to give him a name, was from Tennessee. One day when he wanted to visit home, he asked if Pops would like to tag along for the ride, so Pops did. Cloyce took the first shift driving, so Dad settled into the passenger's seat and promptly feel asleep.
He was eventually woken up by an odd sound. It was kind of between a rhythmic slap and thwap, slap-thwap, slap-thwap, slap-thwap, all in pretty quick succession. He raised his eyes to see that the noise was caused by the mud flaps of the truck in front of them. Cloyce was cruising along at 60 miles per hour about eighteen inches behind a semi trailer.
Pops was self aware enough to not shout out and maybe cause an accident. He raised himself, yawned, and asked pointedly, "Hadn't you better back off a bit, Cloyce?"
"I'm fine."
"I'm. Not." Pops had responded just like that, two one word sentences. He then continued similarly. "Back. Off."
Cloyce backed off about two feet.
A restaurant soon loomed in the distance, and Pops said to pull over, he was hungry. When they parked, he demanded the car keys. "Why?" Cloyce demanded.
"Because I never want to see a speeding truck that close again on purpose!" Dad drove the rest of the way to Tennessee, and home too. I'm not sure he was ever again a passenger of ol' Cloyce.