On the pesedrian warning system, the National Highway Transportstion Safety Administration has 157 pages of sleep inducing text on the matter: https://www.nhtsa.gov/sites/nhtsa.dot.g ... ements.pdf
Out of curiosity, I looked up the statistics on car - pedestrian collisions. In 1999, NHTSA reported 6,000 collisions in the US: https://one.nhtsa.gov/people/injury/res ... 09012.html. EVs currently make up about 1% of cars on the road in the US, so there are probably on the order of 60 pedestrian entanglements with EVs in a given year. National Public Radio reported on car - pedestrian accidents, and stated there is about a 10% chance of the pedestrian being killed in collisions less than 20 MPH: https://www.npr.org/2017/03/30/52208550 ... ian-deaths
Bicyclists are also potential targets of quiet EV provoked crashes. Numbers are for vehicle crashes in general are available here: https://www.npr.org/2017/03/30/52208550 ... ian-deaths
If EVs and ICEs were equally dangerous to pedestrians, then about five people a year in the US would be killed by EVs. NHTSA’s report above claims a quiet EV is 1.18 times as dangerous to pedestrians and 1.5 times as dangerous to bicyclists. That suggests PWS will save about one to two people per year on average in the US.
It seems like there are probably more effective and less expensive ways to improve safety than PWS: for example education, or mobile phones that detect vehicles (not just EVs) approaching, then generate an alert. Of course if you are the person PWS saves, then cost is no object.