These questions turn on category and conduct: adult or under 18, ordinary adult or under 21, mounted interaction or hand-held use, numeric alcohol level or actual impairment. Identify that branch before relying on a familiar number.
Separate device rules by age and interaction
For an adult driver, proper mounting and the size of the interaction both matter. The general rule bars holding and operating a wireless phone or electronic communications device. A properly mounted device may be operated with one swipe or tap of a finger. Holding it briefly, removing it from the mount or entering a multi-step message falls outside that narrow interaction. Temporary traffic stops do not convert hand-held operation into mounted use.
| Branch | Rule to apply |
|---|---|
| Adult device use | Keep the device properly mounted and limit operation to one swipe or tap. |
| Driver under 18 | Wireless phone and electronic communications use is generally barred even hands-free, apart from specified emergency purposes. |
| Ordinary adult alcohol level | The per se figure begins at 0.08 percent alcohol by weight in the blood. |
| Driver under 21 | The measured rule begins at 0.01 percent on a qualifying test. |
| Drug or combined impairment | Actual prohibited influence does not wait for the ordinary adult alcohol number. |
| Container on the driver | Open, broken-seal or partly consumed alcoholic-beverage containers fall within the possession rule. |
A driver under 18 follows the stricter age branch: wireless phone or electronic communications use is generally prohibited while driving even when hands-free, except for the specified emergency purposes. For alcohol, do not merge two different categories. The ordinary adult per se threshold is 0.08 percent. A person under 21 is subject to the measured 0.01 percent rule. Neither figure turns drug impairment into lawful driving. Being under the influence of a drug is prohibited, and so is impairment caused by alcohol together with a drug, regardless of whether the ordinary numeric alcohol threshold has been reached.
For an alcoholic-beverage container, focus on possession and condition. While driving in the covered places, the driver may not possess on the driver's person a container that is open, has a broken seal or has had contents removed. A pocket does not change possession, and choosing not to drink does not restore a broken seal.
The traps
- Holding the device because traffic is stopped at red. The adult limited-use rule still requires proper mounting rather than hand-held operation.
- Treating a mount as permission for a multi-step message. The narrow interaction is one swipe or tap with a finger, not extended entry.
- Applying only the ordinary-adult 0.08 percent figure to a driver under 21. The under-21 rule begins at a measured 0.01 percent.
- Assuming an opened alcoholic-beverage container is harmless when the driver does not drink. Possession on the driver's person is enough when the container is open, has a broken seal, or has had contents removed.
Try it
A 17-year-old driver wants to make a nonemergency hands-free phone call while driving. No emergency exception applies. What is the California rule?
- The call is allowed if it lasts less than one minute and remains hands-free
- The call is allowed whenever the phone is mounted
- The call is allowed if no passenger is present
- The call is not allowed because it is nonemergency device use
Which situations are prohibited by California's drug-impairment rule even when the ordinary adult alcohol number is not reached? Select all that apply.
- Driving while impaired by a drug
- Driving unimpaired after taking a nonimpairing medicine
- Driving under the combined influence of alcohol and a drug
- Driving unimpaired with an ordinary adult alcohol reading below 0.08 percent