YSK that if your turn signal is blinking unusually fast (like 3 or more times a second), it generally means you have a bulb out.
Why YSK: Your signals alert other drivers as to what you're doing; a signal bulb costs a few bucks and is usually a quick and easy repair to do yourself (consult YouTube); and any place that regulates motor vehicles probably requires you to have working turn signals. So knowing when and how to replace a burned out signal bulb...