One problem related to back up alarm has been reported for the 2010 Toyota Prius. The most recently reported issues are listed below.
Narrative description. Not a failure but a safety prevention measure 2010 Toyota Prius 1. Event: when backing up the vehicle runs on battery power-hence it is silent when backing up. The vehicle in busy parking lots (walmart) goes unnoticed. 2. Failure: I have surprised people who are distracted and don't notice me until they nearly walk into the side of the vehicle. They don't hear the car. 3. Failure correction: a back-up warning device should be installed to alert pedestrians (blind folks, neighborhood kids, pets, etc) of a silent, backward moving vehicle approaching. There is several blind spots inherent to the Prius when backing. Helping others to notice you seems like "an ounce of protection that is a pound of cure" that is measured in a saved life or crippling injury.