Subjectivity of the Law

Quick entry tonight, since I really should be sleeping right now. Watched Star Trek: Nemesis tonight at Cam’s. It’s the first time I’ve seen the Next Generation crew in anything for a while. I’m not a huge trekkie, but I did watch the majority of the Next Generation series. I’ve seen two episodes of Deep Space 9 and one of Voyager, but in that short time I’ve given them they didn’t manage to hook me. Enjoyed the film — was kind of shocked to find out Brent Spiner (who plays Data) actually co-wrote the screenplay. That’s kinda cool.
Anyhow here’s the question of the day. Would you agree that driving a vehicle when you’re sleep-deprived constitutes impaired driving? If yes, then how do you deal with the fact that another form of impaired driving — driving under the influence of alcohol — carries a stiff penalty (a fine/jail time and impounding your car for 30 days in BC, a US$10,000 fine in Florida) whereas driving sleep impaired does not? Both put the lives of others besides yourself at risk.
I think there should be penalty for driving when you’re sleep impaired, but the question raised is, how does one measure this objectively?
One idea would be to have the driver rate his or her own fitness to drive. During a conversation with Cam and Melissa this evening I suggested a sort of “contract” the driver enters when they want to turn on the car, say, a button labelled “Yes, I am fit to drive a vehicle in my present state”. If the driver were to get into an accident and this button were hit, the consequences of the accident — say the type of insurance coverage you’re eligible for — would be different. I think the button would be somewhat difficult to implement in practice though — it would lose its meaning once people start hitting it via muscle-memory.
What do you think? Should drivers be held accountable to the same consequences for all forms of impairment? Why or why not?