Automatic stop activated at traffic light. When the brake was disengaged, the star would not start. The occupant was stalled at the traffic light during rush hour in a thunderstorm with limited visibility for approximately 15 minutes. Winter Haven Police Department was dispatched but did not arrive probably due to other weather-related traffic situations. After that time, the engine did start and was moved into a lot without incident. The good Samaritan that assisted stated he had just stopped down the street on another disabled vehicle in traffic due to malfunctioning auto stop/start. Here is the issue. The alternator and battery have both been checked twice and were in proper order. The OE battery was in use. There was no warning to indicate any issue with the batter. In fact, the Subaru app was reporting the vehicle was operating normally while the vehicle was dead in the road. I work with a local law enforcement agency and have worked fatal crashes on that road. It is unacceptable for the vehicle to not have some type of redundant system to warn owners that the vehicle battery is failing before they are thrust into a possible deadly roadway breakdown.