APPROACHING A STOP LIGHT MY VEHICLE CROSSED A ROUGH PATCH OF ROAD WHILE APPLYING THE BRAKES. WHEN I HIT THE ROUGH SPOT MY BRAKE PEDAL WENT TO THE FLOOR AND VEHICLE WAS NO LONGER BRAKING AS INTENDED. VEHICLE SPEED WAS APPROXIMATELY 45 MPH AT THE TIME OF THE INDECENT. THE LOSS OF BRAKES CAUSED ME TO REAR END THE VEHICLE IN FRONT OF ME. THE PROBLEM HAS NOW BECOME INTERMITTENT BUT SEEMS TO BE RELATED TO THE ABS AND OCCASIONALLY THE BRAKE PEDAL WILL GO SOFT AND FEEL AS IF THERE IS LITTLE TO NO RESPONSE FROM THE BRAKES.