THE STEERING AND TRANSMISSION LOCKS REQUIRED ON NEW CARS SINCE 1968 ARE INEFFECTIVE BECAUSE THEY DEPEND ON THE IGNITION LOCK WHICH CAN BE EASILY REMOVED. A FEDERAL BUREAU OF INVESTIGATION STUDY CONDUCTED BETWEEN 1972 AND 1975 SHOWED THAT MOST CARS ARE STOLEN BY REMOVING OR BREAKING IGNITION LOCKS, USING A PICKING TOOL, OR USING THE ORIGINAL KEY CARELESSLY LEFT IN THE IGNITION. OUT OF THE 36 DEVICES TESTED, THE LOCK TECHNOLOGY GML1 DESIGNED FOR GENERAL MOTORS, AMERICAN MOTORS, AND CHRYSLER CARS CLEARLY OFFERED THE BEST PROTECTION. BASICALLY A REPLACEMENT CYLINDER FOR THE ORIGINAL IGNITION LOCK, THE GML1 IS UNPICKABLE AND PROTECTED BY STRICT KEY CONTROLS. HOWEVER, IT MUST BE USED ON CARS WITH CAST METAL HOUSING AROUND THE STEERING COLUMN THAT CAN WITHSTAND PHYSICAL ATTACKS, SYSTEM INTERRUPTERS TEMPORARILY DISABLE SOME VITAL AUTOMATIVE FUNCTION, SUCH AS SHUTTING OFF THE FLOW OF FUEL TO THE CARBURETOR, AND ARE DISARMED BY A HIDDEN SWITCH. THE GENERAL 7827 AND FUEL-LOCK 200 WERE THE TOP-RANKED SYSTEM INTERRUPTERS TESTED BY CONSUMER REPORTS AND WOULD PROVIDE GOOD SECURITY IF THE THIEF COULD NOT FIND THE DISARMING SWITCH. ALARM DEVICES ASSUME THAT A LOUD SOUND WILL DETER A THIEF, BUT THIS COULD DEPEND ON WHERE THE CAR WAS PARKED OR THE TIME OF ATTEMPTED THEFT. TRUCK-LOCK-REINFORCEMENT PLATES AND PAGING SYSTEMS WERE ALSO TESTED, BUT NOT RECOMMENDED. INSURANCE COMPANIES COULD ASSIST IN AUTO THEFT PREVENTION BY REDUCING PREMIUMS ON CARS WITH ANTITHEFT DEVICES. ALL DEVICES TESTED ARE LISTED WITH MANUFACTURER AND PRICE IN ORDER OF THE QUALITY OF PROTECTION THEY PROVIDE. (MJM)