Visible crew/equipment: After the bikers finish revving their engines (when they first arrive in town) there are a couple of close-ups of some of the bikers. One of the bikers starts unstrapping his headgear, as he does this four bright stagelights are reflected in the helmets visor.
Continuity mistake: After Roop drives the police car through the trailer, Charlie in the passenger seat leans back and you see a neck injury. Look at Roop and you notice he is wearing a black jacket, but then only shorts as he reports the incident on the radio.
Continuity mistake: When the first car crashes at the start the bonnet is hanging off, one of the policeman pulls it off and it lands on the ground upside down, when the car pulls away the bonnet is now the right way up.
Other mistake: When Jessie realises that her baby is missing, she runs out into the yard, stops and does a slow 360 turn before looking forward again. She then hears the Toecutter's voice, looks to her right and sees all the knightriders, including one holding her baby. So somehow in that slow 360 turn she did previously, she somehow managed not to see 15 knightriders standing close to her.
Continuity mistake: As the cop car slides after missing the running felon, the car is shown hitting the sign post, smashing a blue light, then the city names are seen, then the sliding car is hitting the sign post again, and again smashing the blue light.
Continuity mistake: When the semi that kills Toe Cutter is seen, the flat, painted shield it suddenly sports for the stunt is gone as Max rolls by after Toe Cutter is killed.
Continuity mistake: Before Max gets hurt by the bikers, he walks out from his car and stands some feet away from it, then he shoots one biker and stands up, but he is now further from the car.
Continuity mistake: When the bikers get Max's baby the sun changes in every shot.
Continuity mistake: When Max gets shot by the bikers the sun changes in every shot.
Continuity mistake: When Goose has an accident on his bike the sun changes between shots.
Continuity mistake: In the opening chase sequence, while the Nightrider is being chased by two Main Force Patrol, the sun changes in almost every shot.
Plot hole: Near the end of the opening chase, the caravan and the pick up truck are completely blocking the road, making it impossible for the Night Rider to pass the way we see him do.
Other mistake: At the end of the opening chase, there is a sudden flaming rocket-like burst from the back of Nightrider's car. Other shots of the rear showed no nozzles for this.
Revealing mistake: After Max takes up the chase and is on Nightrider's tail, you can see that the driver of the cop car is a stunt driver, as he appears to have a hat on. Also, there appears to be a helmeted figure in the passenger seat where there is supposed to be nobody.
Continuity mistake: Towards the end of the opening chase, when the police car flips over, just before this you can see the stunt driver in the car and the passenger is missing, not even replaced by a dummy.
Continuity mistake: When the Toecutter is talking to Johnny The Boy at the beach, the man behind in the army style overcoat has his hand in and out of his pocket, depending on the angle.
Continuity mistake: When Max first gets in his car at the start, he listens to the chase on the radio and we see the reflection in his sunglasses showing the bonnet of the car, a yellow road sign, and what looks like a white single decker bus/coach (could be the film crew bus). When he pulls away, none of those things are there. He drives down the road and pulls up, waiting for the Nightrider to appear, and we see the same reflection in the close up to his sunglasses again - sign, bus/coach and bonnet, but the road in front is clear.
Visible crew/equipment: When Goose is interrogating the stoned biker he turns around and says "Take your time Charlie, we've got plenty of it", when he turns you can see the feet of the camera operator reflected in his glasses. It cannot be the other policeman as he is in the other room.
Chosen answer: It was nuclear war. Tectonic plate movement could make ports dry and flood others. None of the movies ever goes into great detail about the apocalypse.
Grumpy Scot