Here are the details from Jar's Flickr page, which has several more photos:
On Thursday, August 19, 1976, at about 7:30 p.m., a tanker truck carrying liquid propane crashed over a guardrail on the I-69 entrance to northbound I-75 just south of the Miller Road exit in Flint Township, Michigan, and exploded. Police speculated that the propane truck driver may have fallen asleep at the wheel.
The propane truck driver, an auto haulaway truck driver, a Flint woman, and a mother and daughter from Grand Blanc, were seriously burned in the accident. As many as 25 other cars were burned, but none of their drivers required hospitalization.
The propane tanker hit a guardrail on the I-69 entrance ramp to northbound I-75, tumbled over it, and exploded. The rear portion of the tank was blown a quarter of a mile away. The truck cab and the driver were blown back to the I-69 entrance ramp to I-75, about 50 feet above the gully where the tanker exploded.