The benefits of hybrid cars have been outlined and debated exhaustively. However, the National Federation of the Blind will testify next week on the dangers hybrid vehicles in silent mode pose to the blind, and other pedestrians. So called "full hybrid" cars, such as the Toyota Prius, and the shut off their combustion engines and rely on propulsion from quiet electric motors under certain low-speed driving conditions. According to the NFB, "hybrid vehicles are virtually silent when accelerating and decelerating, making it impossible for blind individuals to detect their presence". To address the issue, Maryland State Senator Norman Stone is proposing a bill aimed at requiring all vehicles sold and licensed in Maryland to emit a minimum sound level at all times.