A VEHICLE STOPPED SUDDENLY AHEAD OF ME ON THE BAY BRIDGE NEAR SF, AND EVEN THOUGH I HIT THE BRAKES HARD, THE CAR DID NOT STOP AS FAST AS I FELT IT SHOULD HAVE. I DID NOT THINK ANY MORE ABOUT IT AFTER THE CAR WAS REPAIRED, THEN LAST WEDNESDAY, 10/05/11 I NEEDED TO MAKE AN EMERGENCY STOP ON THE FREEWAY. AFTER HITTING THE BRAKE WITH BOTH FEET, I WATCHED HELPLESSLY AS THE CAR SLOWED BUT DID NOT STOP UNTIL I HIT ANOTHER VEHICLE. THESE ARE THE ONLY TWO 'REAR END' COLLISIONS I HAVE HAD IN OVER 30 YEARS OF DRIVING. I KNOW THAT EITHER OF MY PREVIOUS TWO CARS COULD HAVE EFFECTIVELY STOPPED IN THE DISTANCE GIVEN. I AM NOT SURE THE CAR WILL BE REPAIRED AGAIN, BUT IF IT IS REPAIRED I WILL NEVER DRIVE IT AGAIN. *KB