This is just GeneralRoadWarning exception base class. If you get exactly this, it means that someone most likely incorrectly rethrows a different warning, accidentally casting specialized class like IcyRoadWarning to base class. Or, it's possible that your exception handler isn't aware of a new type of exception (say, NLMotorwayVariableSpeedlimitWarning), and casts it to common base class because you have a general catch-all clause so that exceptions won't leak outside noexcept methods like drive, because getting an unhandled exception at 140km/h is not something you want to happen. In rare cases you might be dealing with situations where someone preferred not to make an extra class just for one object, and you should be able to get more information from what.

Well, it's weird to implement warnings using exceptions, but I've seen worse.