David's tiny car overheats as he desperately speeds away from the truck. The mad truck driver is now more intent than ever on killing him. David realizes that he can't outrun the powerful vehicle and prepares for a last stand. He spins around to face the truck, and speeds toward it as fast as his vehicle will go. David opens the door and leans out of it as the two vehicles speed toward each other. At the last moment, David leaps out of the car and lands on the road, but his car doesn't stop. Its momentum lets it continue moving, and David's car slams at high speed into the front of the truck, and explodes. The car's flaming carcass blocks the trucker's view of the road, and David watches from the sidelines as the truck careens over a cliff. Truck, car, and trucker smash into the unforgiving rocks below, and the truck is dashed to pieces along with its driver. Exhausted, David steps toward the cliff, and looks down upon the charred remains of the truck. The scattered bits of the truck settle into the dust, and all is quiet. David collapses, and continues to stare at the wreckage as the credits roll.
Jack
Answer: At that point in the film, the protagonist David Mann is ready to confront the truck driver. When he sees the old Peterbilt truck outside, David mistakenly assumes the truck driver has already entered the diner, so he confronts a likely suspect that he sees at the counter (but he has misidentified the man). The misidentified man takes offense and punches David out. By the time he recovers his senses, David sees the old Peterbilt truck leaving the parking lot. Which means the actual homicidal truck driver never entered the diner in the first place and was waiting outside the whole time. If David had first gone outside to the Peterbilt, there was a good chance the waiting homicidal truck driver would have killed him right there, and the story would have abruptly ended. So, David's misidentification of the truck driver allowed the film to move ahead into its next act.
Charles Austin Miller
Yes, I get why the filmmakers did that, but I still think it is a plot hole. If the Dennis Weaver character was afraid of getting killed by the truck driver, I doubt he would have confronted him in the cafe.