The police cruisers seen during the finale were real Houston Police squad cars. Ford LTD Crown Victorias were used by HPD from 1983 - 1987; the last use of these squads was in 1993.
The events in the film take place during a time frame of less than 24 hours.
The finale where Cohen rams a roadblock is actually the off-ramp from Interstate 45 to McKinney Street. The building in the foreground is the Houston City Hall Annex, located at 900 Bagby.
Roy Scheider was cast as "Cohen" late in the pre-production phase after Gene Hackman and John Cassavetes passed on the role.