Horrified onlookers stood by helplessly yesterday as a runaway automobile backed over its elderly owner, backed over her again, and then circled next to the dying woman for more than 15 minutes.

The runaway 1977 Ford Thunderbird apparently has the type of transmission which the National Highway Traffic Safety Administration (NHTSA) has warned can slip from park to reverse without warning.

Sixty-seven-year-old Amy Selle was barely alive when paramedics arrived at the accident scene. They found 30 to 40 people gaping ghoulishly at the driverless car as it backed round and round a few feet from Selle. The woman died minutes later.

The car was traveling so fast - 15 to 25 miles per hour - that it took fire department officials 15 minutes of repeated efforts to stop it.

NHTSA warned owners of 1971 to '78 Ford passenger cars that C6 and FMX transmissions may slip from park to reverse. After checking the Florida car's identification number the Ford Motor Co. said the car apparently has either a C6 or FMX transmission. The NHTSA has received reports of 23 deaths, 259 injuries and 777 accidents allegedly caused by the defects, a spokesman said.

Highway patrol spokesman said they could not determine whether the gear had slipped from park to reverse.

Told about the accident, NHTSA spokesman Irving Chor said "that's the typical report of a transmission that slipped."

Fire department officials said Selle had stopped by the roadside to pick up a friend. She got out of the car, apparently thinking the gear was in park but when she got out the car moved backwards. She lunged inside and grabbed at the steering wheel.

But the open door knocked her down into the path of her car, which had pivoted when she turned the wheel.

Paramedics said the car apparently struck Selle twice, fracturing her skull. Then it sircled, neatly clipping the corners of an entire intersection.

Fire officials finally stopped the car when one man leaped inside as another held the door open.