TREAD SEPARATED FROM LEFT REAR TIRE WHILE DRIVING 40MPH. TIRE BLEWOUT. THIS CAUSED VEHICLE TO LOSE CONTROL & CROSS OVER FOUR LANES OF HIGHWAY TRAFFIC. MANAGED TO STOP VEHICLE, AND CHECKED TIRES. NOTICED STEEL BELTS WERE SHOWING THROUGH AFTER SEPARATION. P245/75R16 ON 1996, CHEVROLET, SUBURBAN WITH 42,000 MILES.*AK