Did you intend to reply to me? The reason we are trialing these systems on public roads is because that is where they must operate in order to make sense. It's

Did you intend to reply to me? The reason we are trialing these systems on public roads is because that is where they must operate in order to make sense. It's not about safety alone. To respond to your tangent: Breathalyzers are not all that reliable, nor is GPS localisation... And a national speed limit would mostly reduce revenue (not to mention the new problems regarding who is liable for maintaining the limit correctly). There is a great history of implementing practical safety requirements, maybe not the first globally, but when it becomes practical to adopt something we generally do.