DRIVING VEHICLE ABOUT 35MPH & STARTED TO APPLY BRAKES; HEARD LOUD POPPING NOISE; AFTER LEAVING TOLL BOOTH, ANOTHER VEHICLE CUT OFF SEBRING; HIT BRAKES HARD, HEARD POPPING SOUND; BRAKES DIDN'T CATCH; WENT INTO SPIN & HIT RETAINER WALL, FRONT END CAME UP & SMASHED WINDSHIELD; SEAT BELT CAME UNLATCHED UPON IMPACT; AIR BAG DID NOT DEPLOY. *AK