Recently Google's captcha asked me to mark all the traffic meters on the photos, and amongst the choices was a photo of a mailbox. It didn't let me through until I marked it as a meter as well.
Good luck to whatever self driving car they are training using this data.
4chan users already used to do this for the old text based ReCaptcha. The idea was everyone put in a particular racial slur (they're not very imaginative) for the second word. I doubt it had any impact.
Well that might be my handiwork! About half the time I have to do an reCaptcha i mislabel one of the photos. Because I’m not being paid, I’m being held hostage to an automated system and I will rebel.
Good luck to whatever self driving car they are training using this data.