This slip-up is at the beginning of the movie when Montgomery is at the police academy training to become a police officer. After the chase of the training "Director/ Trainer" Montgomery opens his door and hits him with it then jumps out...there you can see that the police car had lights on it..but after Montgomery puts cuffs on the trainer and yells "Time!" the car that supposedly was being driven by him and crashes into the barrels, does not have any police lights on top.