It should be noted that it isn't a matter of safety, but one of legality. You are on a road and traveling at 10 mph under the speed limit -- are you at a safe speed? 10 mph over -- are you at an unsafe speed? Don't know; all you can say is that you are at a legal or illegal speed. It's uncertain at best that these devices will add to safety; they will make it possible for your insurance to deny or lessen your claims, however. That's what they're interested in -- if they get that through safety, that's fine with them, but if they get it through something that has no effect on safety, that's fine with them too. These boxes are about bottom lines, not about safety.