Answer: A concept designed to minimize three-month summer learning losses, year-round education maximizes the use of public facilities by dividing the school attendance days into rotating instruction and vacation segments.
If I'm understanding you correctly (sorry, I'm new at this) It sounds like you are describing an accident that either didn't actually happen, or was minor compared to what could have happened. I would call this a "near miss" or "close call"
Explanation:
For example: I had a near miss today when a dog ran out in front of me.
Or: He had a close call when his foot almost slipped over the edge of the cliff.