Dexter Hoover is the Piston Cup flag truck.

From the Blu-Ray Guide: As a youngster, Dex dreamed of being a real race car. A 4 cylinder compact pickup isn't exactly designed for the racetrack, but Dex found a way to put himself in the middle of his favorite sport. He climbed the ranks from selling pennant flags in the stands to top flagman on the circuit. His unorthodox caution flag pattern is a thing of beauty. If it weren't for Dex, the races would never start, and they'd never end.