UNMARKED PATROL VEHICLES ARE PART OF THE HERITAGE OF THE ILLINOIS STATE POLICE. EARLY SQUAD CARS WERE PLAIN, DARK VEHICLES WITHOUT CONSPICUOUS WARNING LIGHTS. TODAY, SQUAD CARS ARE HIGHLY VISIBLE, OFTEN THWARTING EFFORTS TO STOP SPEEDERS, AND LEADING THE ILLINOIS STATE POLICE TO REVISE ITS UNMARKED PATROL CAR PROGRAM. SIX YEARS AGO, MARKED PATROL CARS, OR SPORT COUPES KNOWN AS COVERT CARS, FRIGHTENED MANY MOTORISTS. TODAY, UNMARKED ILLINOIS STATE POLICE TRAFFIC UNITS ARE REGULAR FLEET PATROL VEHICLES, PASTEL OR WHITE, WITH LICENSE PLATES REFLECTING THE ASSIGNED TROOPER'S DISTRICT AND PERSONAL NUMBER AND WITH CONCEALABLE WARNING LIGHTS. EACH DISTRICT ALLOWS 15 PERCENT OF ITS PATROL FLEET TO USE UNMARKED CARS. CARS ARE ON 24-HOUR UNMARKED PATROL, AND ASSIGNMENT IS GIVEN TO EXPERIENCED OFFICERS WITH PROVEN JUDGMENT AND PUBLIC RESPONSE WHO HAVE DEMONSTRATED A HIGH ACTIVITY RATE. PHOTOGRAPHS ILLUSTRATE THE ARTICLE. (MJW)