I don’t think it’s the silence that makes car and other vehicle dangerous… It’s the fact that the road is there turf and you as a pedestrian or a cyclist have to be extra vigilant to cross. It’s regrettable most cities are designed that way. Plus, I am almost certain electric buses, just like trams, have a ring bell to make extra noise warning distracted pedestrians. Finally, it’s always the responsibility of the driver (even you as a car driver) to be vigilant of his surrounding, the driver is in charge of the safety of people all around him as he his in control of a massive, deadly machine.
It doesn’t scratch the glass, even when applying quite some force. The blade dulls pretty fast, it probably doesn’t have the hardness to damage the glass.