The biker who ran into Green & White Highway sign, clothes-lining himself at the neck-shoulders would have been decapitated traveling at any rate of speed.
At one point, Archer in the blocker car overhears his mother in the bus complaining about his uselessness because Cyril in the bus accidentally held down the talk button on the CB radio. Archer then tells the others in the bus that someone over there is holding the talk button. However, the talk button on a CB switches off the loudspeakers, so the others should be unable to hear him say it.
Shortly after passing through Texarkana, Cyril says that they have about 100 miles to get to Austin. The distance between those two cities is more than 350 miles.