Codrivers are more than passengers: It's the codriver's job to keep tabs on the gauges, make sure the truck stays on course, and to be the first one through the window if there's a flat tire to change. "Do you need me to do anything?" I asked Matt. "Do you need me to call out the turns?" "I know the course well, so don't worry about that," he replied. "Just keep an eye on the engine temperature, and watch the rearview monitor to see if anyone's coming up behind us. Other than that, just sit back and enjoy the ride."