WHILE DRIVING ON THE HIGHWAY (MORNING TRAFFIC MOVING AT SPEED LIMIT - 65-70 MPH) I SMELLED SMOKE. IMMEDIATELY FOLLOWING THIS THERE WAS A THUD AND THEN THE CHECK ENGINE, LDW AND OTHER LIGHTS ILLUMINATED ON THE DASH, ALONG WITH AUDIBLE ALARM SOUND. SMOKE WAS NOW VISIBLE, COMING FROM THE ENGINE (UNDER THE HOOD). I WAS ABLE TO MOVE FROM THE MIDDLE LANE TO THE RIGHT LANE/EXIT LANE AS I KNEW I NEEDED TO PULL OVER IMMEDIATELY. SINCE I WAS IN AN EXIT LANE THERE WAS NO REAL SHOULDER AND I STARTED DOWN THE EXIT RAMP. THE SMOKE WAS VERY STRONG AT THIS POINT. I WENT TO DEPRESS THE BRAKES TO SLOW DOWN ON THE EXIT RAMP AND TRY TO PULL THE CAR OVER BUT I HAD NO BRAKES. THE BRAKE PEDAL WENT RIGHT TO THE FLOOR. I HAD LIMITED STEERING CONTROL AND WAS DRIVING ERRATICALLY TRYING TO KEEP CONTROL OF THE CAR WHILE ON THE EXIT RAMP. I TRIED TO PUT THE TRANSMISSION IN PARK - NO EFFECT TO SLOW THE CAR. I TRIED TO POWER THE CAR OFF - DID NOT WORK. I HAD TO DEPRESS THE EMERGENCY BRAKE TO STOP THE CAR. IT TOOK OVER 100 FEET TO STOP THE CAR (LUCKILY NO OTHER CARS ON THE EXIT RAMP) AT WHICH POINT I COULD PULL OVER ON THE SIDE OF THE ROAD. AT THIS POINT THERE WAS SMOKE BILLOWING OUT OF THE ENGINE AREA, SMOKE COMING IN TO THE CAR. I CALLED 911 AND THEY RESPONDED IN ABOUT 5 MINUTES. AFTER I GOT A SAFE DISTANCE FROM THE CAR I COULD SEE FLAMES COMING FROM THE BOTTOM OF THE ENGINE. FROM THERE I COULD SEE THE FIRE START TO GROW IN THE ENGINE COMPARTMENT AND ONCE THE FIRE DEPT ARRIVED IT WAS ENGULF