When Roman and Burgess are first seen staking out the pipe-bombers' house, the interior of the squad car is light-colored, and the seat-belt cover over Burgess's right shoulder is missing. Later, during the same stakeout, the interior of the car is black, and the seat-belt cover has reappeared.
During the opening car explosion scene, Voight calls 911 and gives his name and badge number. Chicago police have a star and not a badge as in New York City. A veteran officer would not say badge.