Like all these things, it's when something goes wrong that, really, it will be tested, and "going wrong" means that it would generally be an accident. Sadly, even with experienced fire staff, police staff, and ambulance staff, serious accidents still occur, because, actually, having the ability to go through red lights, to go to speed, or to go into lanes or places where the general public would not be expecting to see a car, does create issues. 