Yea, there are many cars that are almost silent, and not just hybrids. When my Tercel's exhaust is really tight and not leaking anywhere, it's near silent at idle, so the only sound a pedestrian would hear is wheel noise, which is the same that a Prius would make.
I think people need to realize that they're not the only ones on the road - drivers, pedestrians, and cyclists. You can't rely on sound when you're driving or walking, you need to look around as well.
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