In Washington, driving off to the side of the roadway to “sleep it off" after drinking and/or drugging can get you charged with a crime. That crime is being in physical control of a motor vehicle while under the influence of alcohol and/or drugs. The penalties are the same as for a DUI in every respect.
It is important to know that the state legislature has provided a “safe harbor" for people who do this. If one is “safely off the roadway" prior to when law enforcement arrives, then, if the crime is charged, this defense is available.
Two points should be made (on top of the obvious, bombproof advice to avoid driving after drinking .) First, the further off the roadway one is, the better. Second, the more inaccessible the vehicle’s ignition key is, the better. If one’s intent is to not endanger the public by deciding to pull over and sleep it off, great. But one should do everything in one’s power to make the vehicle more like a bed and less like a car. A key in the ignition, whether the motor is running or not, is not ideal. Better would be to lock the ignition key in the trunk, or even hide it someplace by the roadside. If you can safely leave the car and start walking home and/or call for a cab or a friend to pick you up, that is the best by far.
Police and prosecutors are aware of the “safely off the roadway" defense and are less likely to charge a person who truly seems to have made the decision to save lives by correcting the mistake of driving under the influence. They might still do so, though, and opt to let a jury decide whether a driver did the right thing. But remember, one always has the right to not speak to the police, not to offer a roadside breath sample, and not to engage in roadside field sobriety tests. These rights should be politely but firmly exercised.