A United States motorist has recorded a blood-alcohol reading of .708 - more than 14 times the Australian legal limit of .05.

The Rapid City Journal news website reported that the woman, 45, was found passed out behind the wheel of a allegedly stolen delivery truck parked on an interstate highway.

Checks with local and state testing laboratories suggested the reading was a state record, the journal reported.

One researcher said he had measured a blood-alcohol sample that tested .56, and a chemist told lawmakers he recalled a reading of .53.

State research indicated that a blood-alcohol level of .40 was considered lethal for about half the population.

According to the website, the woman was hospitalised and freed on a bond after she was discovered in the vehicle on December 1.

Two weeks later, after failing to appear in court, she was located in another allegedly stolen car sitting near a different highway.

She was charged with a second offence of driving under the influence of alcohol and placed in custody.

The legal blood-alcohol limit in South Dakota is .08.

Last year in Victoria, a woman was reported to have recorded Victoria's highest blood-alcohol reading for a female when she blew .462 - more than nine times the legal limit.