WHILE DRIVING ON A FREEWAY ENTRY RAMP OUR 2007 PRIUS' BRAKES FAILED TO ENGAGE WHEN THE BRAKE PEDAL WAS PUSHED. NO BRAKING ACTION WAS FELT AND OUR CAR RAN INTO THE REAR OF ANOTHER CAR ON THE ENTRY RAMP. ESTIMATED SPEED WAS ELEVEN MILES PER HOUR ACCORDING TO THE POLICE REPORT. THIS WAS NOT A SKID SITUATION AS THE SPEED WAS SO LOW. THE BRAKES SIMPLY FAILED TO ENGAGE. OUR CAR IS CURRENTLY BEING EVALUATED BY OUR INSURANCE COMPANY.