Someday, we may all be used to silent cars, but currently a person's brain processes a silent car as turned off and no danger. I had my first electric car in the mid '70's - one my dad and I built. After several incidents of pedestrians stepping in front of the car - just as I was about to start accelerating, we added a small buzzer to act as "engine noise" whenever the car was armed and dangerous. It was a simple fix and it worked. There may be other solutions, but this one does not require reprogramming people.
(add your own thoughts)
It should include things like this: Interactive Art using FlipBits. Full Disclosure: Yes, it may be a shameless plug. But you asked for my opinion.
"Quaker Oats objects to the business name 'Quaker Oats Christmas Tree Farm' and demanded the Quakers immediately stop all use of the 'Quaker Oats name' because it says using the trademark is misleading."
The problem is that isn't the name of the farm. The Quaker's response is brilliant.