THE BRAKING SYSTEM DID NOT FUNCTION CORRECTLY RESULTING IN A CRASH. BRAKES WERE HARD AND COULD NOT BE DEPRESSED WHEN A VEHICLE STOPPED QUICKLY IN FRONT OF ME. TOOK THE CAR TO MAZDA DEALERSHIP AND THEY INFORMED ME THAT THIS IS A KNOWN PROBLEM AND REPLACED THE BRAKE BOOSTER UNDER A "SPECIAL WARRANTY". THIS NEEDS TO BE A SAFETY RECALL, I WAS NEVER NOTIFIED OF THIS SAFETY ISSUE. IT IS IMPERATIVE THAT NHTSB REOPEN THE INVESTIGATION ON THIS PROBLEM AS IT DOES NOT ONLY INVOLVE 2010 AND 2011 CARS AND DOES NOT ONLY OCCUR IN "HIGH AMBIENT TEMPERATURES". VEHICLE WAS IN MOTION AND WAS SLOWING ON AN SLIGHT UPHILL GRADE. VEHICLE IS 5 YEARS OLD AND HAS 53,000 MILES.