ON 4/28/2016 TRAVELING TO WORK FOLLOWING A TRACTOR TRAILER IN A 55 MPH ZONE, THE TRACTOR TRAILER ABRUPTLY MERGED INTO THE RIGHT TURN LANE AFTER A CURVE WITHOUT A SIGNAL LEAVING TWO STOPPED CARS IN MY TRAVEL LANE MAKING A LEFT TURN. I APPLIED HARD PRESSURE TO MY BRAKES AND THE PEDAL WENT TO THE FLOOR. I IMPACTED AN AVALANCHE THAT WAS PUSHED INTO A SMALL COMPACT CAR CAUSING SUBSTANTIAL DAMAGE TO MY VEHICLE AND THE AVALANCHE. THE DRIVER OF THE AVALANCHE WAS TRANSPORTED TO THE HOSPITAL WITH MINOR INJURIES. WHILE AT THE ACCIDENT SCENE I NOTICED FLUID LEAKING UNDER MY TRUCK JUST BEHIND THE LEFT REAR TIRE. THE TRUCK WAS TOWED FROM THE SCENE TO A BODY SHOP WHERE THEY DISCOVERED 2 RUPTURED BRAKE LINES IN BETWEEN THE MASTER CYLINDER AND PROPORTIONING VALVE. ATTACHED PICTURES SHOW SEVERALLY RUSTED BRAKE LINES WITH NO OTHER RUST OR CORROSION ON PARTS IN THE SURROUNDING AREA. INITIAL ESTIMATE FOR REPAIRS ON MY TRUCK WERE $6,371 BEFORE TEAR DOWN.