The answer, as I've argued before, is to scrap the under-the-influence model altogether. Stop focusing on why people drive poorly and start punishing them for driving poorly. A family of four killed when an oncoming car hops the median is no less dead if the driver was a mom distracted by her kids in the back seat, a drunk driver, or a teenager who lost control while sending a text message.
If you want to crack down on highway deaths, pass more severe penalties for reckless driving, regardless of the cause. You could gradually at more punishment for someone who causes an accident, causes injury, or causes a fatality. But the actual breaking of traffic laws should be the crime. When you focus on the cause of impairment, you get problems like Fourth Amendment-stretching sobriety checkpoints, or cops authorized to draw blood along the side of the road. Cell phone and texting bans become another excuse for cops to make pretext stops while drug profiling.