At 100 mph, chances of survival would be extremely remote, even with seatbelts and an air bag.
Without seatbelts, an airbag would be usless at that speed. A person not held in the seat by belts would continue forward over the air bag and into the windshield. Assuming by that time the windshield had broken, the person would continue forward and be ejected. Most likely, they would contact the concrete structure. The final result would be difficult to identify.