I WAS IN HEAVY TRAFFIC ON I-17 NORTH OF PHOENIX AZ. ADAPTIVE CRUISE CONTROL (ACC) WAS SET AND I WAS FOLLOWING THE CAR AHEAD AT THE MAXIMUM DISTANCE SET BY ACC. MY FOOT WAS NOT ON THE ACCELERATOR OR THE BRAKE. I SAW THE PRECEDING CAR'S BRAKE LIGHTS COME ON, AND I FELT MY CAR START TO SLOW. THE PRECEDING CAR STOPPED AND IT BECAME APPARENT THAT MY CAR WAS NO LONGER BRAKING, OR IF IT WAS, NOT HARD ENOUGH TO STOP. I APPLIED THE BRAKES BUT IT WAS TOO LATE AND WE HIT THE CAR IN FRONT OF US AT A SPEED GREAT ENOUGH TO DO $7000 OF DAMAGE TO THE FRONT OF MY CAR. CURIOUSLY THE AIR BAGS DID NOT DEPLOY. PASSENGERS IN THE CAR INCLUDED MY WIFE IN THE FRONT SEAT, WHO WAS THROWN INTO THE SEAT/SHOULDER HARNESS HARD ENOUGH TO KNOCK THE WIND OUT OF HER. SHE COMPLAINED OF CHEST PAINS AND WAS TAKEN BY AMBULANCE TO THE HOSPITAL. NO SERIOUS INJURIES WERE FOUND. MY DAUGHTER IN THE BACK SEAT AND I WERE RESTRAINED PROPERLY BY THE SEAT BELT AND SUSTAINED NO INJURIES. I CONTACTED SUBARU AND TOLD THEM ABOUT THE ACCIDENT. THEY RESPONDED BY TELLING ME THAT THEY WERE SENDING TWO ENGINEERS TO INSPECT MY VEHICLE. AFTER A MONTH OR 6 WEEKS THEY RESPONDED THAT THEIR INVESTIGATION WAS COMPLETE. THEY FOUND THAT 5 SECONDS BEFORE THE CRASH I WAS TRAVELING AT 45 MPH. 1.5 SECONDS BEFORE THE CRASH THE BRAKES WERE APPLIED (DISABLING ACC). THEY TOLD ME THAT THE EYESIGHT WAS FUNCTIONING NORMALLY AND WILL NOT STOP ALL CRASHES. SO SORRY. I BELIEVE THERE IS SOMETHING WRONG, EITHER WITH THE DESIGN OR