SAN FRANCISCO (AFP) - A California appeals court has tossed out a fine for a driver checking a smartphone map to escape traffic, offering a new interpretation in the crackdown on "distracted driving."

A panel of judges reasoned that the summons and its US$165 (S$208) fine applied to holding mobile phones to converse while driving and said nothing of looking at maps on screens for directions.

"We conclude that the statute means what it says - it prohibits a driver only from holding a wireless telephone while conversing on it," the appellate court said in a written ruling available online Friday. "Consequently, we reverse his conviction."

The driver was sitting in congested traffic when a California Highway Patrol officer noticed him using his smartphone. In a subsequent appearance in court, both the officer and motorist testified he was using a smartphone map service.

The driver was found guilty and ordered to pay a fine, then appealed the case.

The ruling in the state that is home to Silicon Valley came as laws and informal codes of conduct are under pressure to adapt to lifestyles in which mobile devices let people be connected to the Internet almost anywhere.

Any potential precedent set by the ruling would be legally limited to California but has the potential to effect how traffic laws are shaped or interpreted in other parts of the country.