A driver in the next lane is moving his lips. Is he on a hands-free cellphone? Talking to someone in the car? To himself? Singing along to the radio?

If lawmakers follow the advice of a federal board, police officers will have to start figuring that out — somehow.

The National Transportation Safety Board said this week that drivers should not only be barred from using hand-held cellphones, as they are in several states, but also from using hands-free devices. No more “Sorry, I’m stuck in traffic” calls, or virtually any other cellphone chatter behind the wheel.

Though no state has yet implemented such restrictive rules, the NTSB’s recommendations carry weight that could place such language into future laws, or motivate the federal government to cut funding to states that don’t follow suit.

Many of the men and women patrolling the nation’s streets and highways wonder how they would sort the criminally chatty from the legally chatty.

“It would be almost impossible to determine if someone was talking on a phone or exercising their vocal cords,” said Capt. Donald Melanson of the West Hartford, Conn., police department, which took part in a national pilot program aimed at cracking down on drivers’ cellphone use. “That would be much more difficult to enforce, almost to the point where it would be impossible.”

A federal law would be like Prohibition – nobody would obey the law.

In California, the state law is already mostly ignored although drivers are sometimes pulled over and fined.

Education about attentive driving will be better than passing punitive regulatory measures.