That's a clever play on words! While the sign is likely intended to be humorous, there is some truth to the statement.
Many people do learn about traffic rules and safety measures as a result of an accident or near-miss experience. Unfortunately, it sometimes takes a dangerous or frightening situation to make us realize the importance of following traffic rules and being mindful of our surroundings while on the road.
However, it's important to remember that learning by accident is not the most effective or safe way to become a responsible driver. Instead, we should all make an effort to educate ourselves about traffic laws and safety measures, and take proactive steps to ensure the safety of ourselves and others while on the road. This might include taking a defensive driving course, staying up-to-date on traffic regulations, and always wearing a seatbelt and driving sober.