AS I WAS APPROACHING THE MAIL BOX AREA IN MY APARTMENT COMPLEX AT APPROXIMATELY 15 MPH, I PUT MY FOOT ON THE BRAKE TO TURN INTO THE PARKING AREA IN FRONT OF THE FOUR METAL MAILBOXES AND PUT THE VEHICLE IN "PARK" WHEN THE VEHICLE SUDDENLY LURCHED FORWARD AND JUMPED THE SIX-INCH, BRICK-PAVER CURB. I CRASHED INTO THE MAILBOX STRUCTURE, COMPLETELY UPLIFTING THE BASE THAT WAS BOLTED INTO THE CONCRETE AND HIT A WOOD TRASH CONTAINER HOLDER. I DEPRESSED THE BRAKE PEDAL HARDER BUT MY VEHICLE WOULD NOT SLOW DOWN OR STOP AND I ALSO COULD NOT CONTROL THE STEERING. I CONTINUED UP A HILL (AT 45-50 MPH) CONSISTING OF TALL GRASS, WILDFLOWERS, ROCKS, ETC., ACROSS A WALKING PATH OF WOODCHIPS AND MULCH, THEN DOWN THE HILL (STILL WITH MY FOOT ON THE BRAKE) GRAZING THE BRANCHES AND LEAVES OF A SMALL TREE BEFORE COMING OFF THE SIX-INCH CURB AND BACK ONTO THE STREET, WHERE I HIT A LIGHT POST. I MANAGED TO LIFT THE PARKING BRAKE, SLAM ON THE BRAKE AGAIN AND THE VEHICLE ROLLED TO A STOP. IT SHOULD BE NOTED THAT NONE OF THE AIRBAGS DEPLOYED.