I don't know how people with vision impairments get past them at all. You have nine poor quality fuzzy images, some of which show part of an item that might, or might not, be a car or a street sign. And then there is the 'is this a car / street sign?' question. I just failed a captcha because an image showed me a thing that I would call a bus. But apparently to a captcha, it's a car. And if the 'street sign' shows a different language or indeed alphabet, sometimes you can't work out exactly what it is. Or it shows you a photo with what are probably cars, but they are tiny and far away!
Aaaaaaaaaaa! Come back, mental arithmetic captchas, all is forgiven!