I HAD CRUISE AT 80MPH ON INTERSTATE HIGHWAY AND DISENGAGED ON EXIT RAMP BY USING THE BRAKE. THE CAR SLOWED BUT I USED BRAKE AGAINN TO YIELD ONTO 4 LANE ROAD AND AGAIN TO CROSS OVER 2 LANES INTO A GAS STATION. I PULLED UP TO PUMP SLOWLY. WHEN I PUT THE BRAKE ON AGAIN TO COMPLETTE THE STOP,THE CRUISE REENGAGED AND THE CAR TOOK OFF. LUCKILY THERE WAS OPEN PARKING SPOT,I AIMED THERE AND CAR JUST KEPT GOING. OVER A CURB, THROUGH ABOUT 75 YARDS OF GRASS AND INTO A FIELD,ABOUT 25 FEET IN. NO BRAKING EVEN THO I TRIED. IN THE BRUSH WAS A CONCRETE BLOCK I HIT THAT CAUSED BOTH PASSENGER TIRES TO BLOW AND THEN THE CAR SLOWED AND WENT TO THE LEFT SOME 5 FEET AND STOPPED. NO AIRBAGS DEPLOYED. I ONLY PLOWED DOWN SMALL BRUSH AND MISSED A TREE IN MY PATH WHEN CAR VEERED LEFT AFTER TIRES BLEW. IT WAS A DRY SUNNY MORNING WITH NO ADVERSE WEATHER CONDITIONS. I HAD ONLY BEEN DRIVING FOR AN HOUR AND HAD STOPPED TO GET GAS AND USE RESTROOM. THEPA STATE TROOPERS CAME BUT SINCE NO DAMAGE TO OTHER PROPERTY AND NO INJURIES, THEY DID NOT FILE A REPORT. USAA INSURANCE NOTIFIED AT ONCE AND TOOK THE CAR. THEY CLAIM IT AS A TOTAL LOSS. I AM BLESSED TO BE OK BUT THIS CRUISE/BRAKE MALFUNCTION COULD HAVE BEEN DEADLY ANYWHERE ELSE. I HOPE YOU WILL INVESTIGATE I WOULD NOT WANT ANYONE ELSE TO EXPERIENCE THIS