When Jim and Grace break into the motel room, they enter room 12. However, when Grace comes out of the room, it is room 11. This is result of a deleted scene that can be viewed on the DVD, where Grace goes into the room 11, thru the connecting door, to find a couple murdered.
After Grace and Jim push the Hitchhiker out of the car, as soon as he is pushed, and shows him outside, you can see Grace leaning out and shutting the door. But when it shows them back in the car, she is still in the back seat, then moves to the front, and shuts the door, although she already did.
The broken windshield of the 442 continuously changes throughout the movie. In some scenes it is slightly broken while in others it is completely shattered.
In the shot when the family car passes Jim and Grace there is a little girl in a car seat. When they come on the car on the side of the road again, the little girl is not in the car nor in the car seat when Grace tosses it out. The little girl is never seen again through out the movie. In the special features section of the DVD is a clip of the news report of the family's murder - the girl's body can be seen in the rear with her brother's body. There are several differences between the news report and the events in the film: It states the family was found off highway 110, but in the film Grace and Jim drove the car to the diner; the children are said to be "between 8 and 12 years old", in the film, the girl is seen in a car seat, far younger.
When Jim and Grace wreck down the ditch, a tree branch goes through the windshield that was broken earlier. But in this scene Jim smacks his head against the windshield and it's completely crack-free after being broken earlier.
When the Oldsmobile 442 flies off the road, the airborne car crashes very hard nose first into the ground. Jim and Grace are not wearing seat-belts yet somehow they manage to remain seated without slamming into the dashboard or windshield.
When the station wagon is hit hard from the rear the young man in the back seat is thrown FOREWORD against the back of the front seat. The impact from the rear would accelerate the wagon and throw the occupants to the rear of the station wagon. Physics/Inertia.
After almost hitting John Ryder in the beginning and then driving away, we can see it raining on the windshield of the car. However, at the speed they are traveling the water should be moving upwards on the windshield due to the air rushing against the car but instead travels downward as if the car was sitting still.
When Jim pours the water on the windshield to get the dead bug off some water hits the camera lens.
In the car chase scene the helicopter pilot radios that another car (the one the John Ryder is in) is approaching. He describes it as a "Late Model" Trans Am, however it is a late 70's model, not a newer one.
When Grace is in the cafe bathroom gathering paper towels, she sees Ryder's truck and moves to lock the door. The problem with that, however, is that the door swings in. The type of lock that's used (bathroom stall lock, just without a latch to slide it into) would only work if the door swung out.
Right before John Ryder shoots Lt. Esteridge in the head, Grace breaks the door off of he armored vehicle and lands on it. Then she screams, "No", but it is clearly visible that her mouth is not moving.
When the car does the 360 spin, you can quickly spot the cameras and crew tied to the roof of the car whilst it's spinning.
When Grace and Jim are hiding in the shack from John Ryder after escaping the police station where they were interrogated, Jim asks Grace if she sees Ryder outside. Grace looks through the peep hole in the shack to look. There is a woman (probably a crew member) clearly visible in the field as the camera pans from right to left.
In the convenience store scene the guys says that Tatum is 15 miles away. Just before they get to the store there's mountains everywhere. There are no mountains or interstates anywhere near Tatum.
Right after Jess crashes his car, he seems to climb a small hill (or out from a ditch). When at the top, he watches the station wagon continue down a winding road -- this is seen from his POV. However, when the POV changes to a side view, the road has changed to a straight one and the hill now goes in an upwards slant.
When Jim talks to the Hitcher he tells him that they are going to Spring Break in Havasu but when he picked up his girlfriend in Austin the Crepe Myrtle trees were in full bloom which does not occur until late spring early summer.