This has been an issue that has been on the table since I first started working in the impaired-driving field 25 years ago. Even back then, when we looked at the evidence there was a lot of interpretation to what was out there. It was not very clear-cut. Not everyone is impaired at a level of 50. You will find impairment on some tasks in laboratory situations; there's no doubt about that. Not everyone is impaired on all tasks at that level. Imposing criminal sanctions on those people just doesn't seemed justified. When you get to a level of 80, yes, virtually everyone shows impairment. That's the level that seems appropriate for imposing criminal sanctions.
Are there reasons to do things with people who are between 50 and 80? Yes. There are enough of them that have sufficient level of risk on the road and sufficient degree of impairment that you should get them off the road to send them a message. It's an early-warning system. Should you do things with people who repeatedly do that? Yes. You should increase the sanctions and you should get them into an assessment, and possibly a treatment or a rehabilitation program. The graded response to impaired driving based on blood alcohol concentration just makes so much sense to us that simply having a level at which it is criminal and a level at which it is not criminal just doesn't make sense to us.