[kuboa]

And they should stop, and err on the side of caution. An anecdotal digression, if you'll allow me: I'll never forget the time when a plastic bag was gently flitting across the highway a friend and I was traveling on, in that nonchalant manner plastic bags usually do, and how we, not giving it even a second thought, drove right through it... Except we couldn't, since it turned out there was actually a small picnic-type propane tank inside the bag, rolling on the asphalt, and our car's motor was totaled by the impact, though thankfully we didn't suffer any serious injuries.

[sitkack]

This is why you never run over anything in a car. Ever.

[cgriswald]

No, they shouldn't. I'm glad you weren't hurt, but your freak accident aside, most plastic bags are just plastic bags and human drivers are not expecting vehicles to yield to them. (There is also a difference between a plastic bag moving on the ground and one flying around.) If we are erring on the side of caution we shouldn't be creating a more probable hazard to avoid a less probable one.

And if we remove humans entirely from the equation what we get is traffic that comes to a stop because none of the vehicles can avoid or get past the plastic bag which floats around more-or-less randomly.