TRAVELING ON ROAD AT POSTED SPEED OF 35MPH APPROACHING A HIGHWAY INTERSECTION. TRIED TO MAKE A NORMAL STOP AND BRAKE PEDAL WENT TO THE FLOOR. TRUCK WENT THROUGH RED LIGHT AND THROUGH INTERSECTION OF A SECTION OF HIGHWAY THAT IS 8 LANES WIDE. IF NOT FOR EARLY TIME OF DAY IT WOULD HAVE BEEN A LOT MORE TRAFFIC AND KILLED SOMEONE. STOPPED TRUCK BY SLAMMING INTO PARK. NO BRAKE WARNING LIGHT PRIOR TO THIS OR AFTER.