> It's not foolproof because people catch on and wipe down their headlights before leaving the bar. There are many reasons it's not foolproof, chiefly among th

> It's not foolproof because people catch on and wipe down their headlights before leaving the bar. There are many reasons it's not foolproof, chiefly among them that leaving a bar is not a basis for knowing that someone is over the legal limit for operating a motor vehicle. The driver might well be a DD.