Other mistake: In the opening scene where Charlton Heston drives into a Deserted Los Angeles, he drives past at least 3 people walking down the sidewalk. The first person he passes is quite visibly holding up the traffic for the shooting. Another can be seen on the left of the screen when Heston puts the tape on. And one more can be seen in the wide shot of the street. Other than this, the film makers did a great of making LA look deserted.
Other mistake: Early in the movie, when Neville wrecks his car he takes the gas can out of his car and starts walking down the street. As he does they switch to a wide view of the city in which you see about three city blocks. When you look at the only "through" street in the shot, there is a car making a left hand turn about three blocks down that street and just behind the car is the freeway overpass with two or three cars passing on it, before the shot ends.