The Jeep CJ5 rolls over so easily, even at low speeds, that it has a higher fatality rate than anything else on the road, including morotcycles according to a study by an insurance organization.

The CJ5 "the most dangerous thing on four wheels. It is probably more dangerous than anything on two wheels as well," said the research director of the Insurance Institute for Highway Safety, a research group supported by the industry.

In crash tests reported in the latest issue of Status Report, a publication of the institute, three of four Jeeps turned over going 22 miles an hour in a 90-degree turn, and three of three flipped over at 32 miles an hour when swerving to avoid an obstacle.

"You cannot get a passenger car to turn over on a flat road -- even at 50 miles an hour, no matter what kind of maneuvers you pull," said Brian O'Neill of the insurance institute. "But many utility vehicles can turn over, and I believe the Jeep is probably the worst case."

American Motors Corp., which manufactures the Jeep, was closed yesterday and spokesmen could not be reached for comment. But in a previous investigation of the rollover tendencies of the Jeep, the company wrote to the National Highway Transportation Safety Administration that "an investigation of vehicle crash data indicates that, in general, vehicles do not roll over due to any inherent tendency toward rollover in the vehicle itself, but rather the rollover is a result of leaving the highway."

A spokesman for the NTHSA said the agency was looking at the insurance institute's tests and would compare those results to tests of their own. A decision about a full-scale investigation has not been made, he said.

"But I would emphasize that this rollover question is not just for the AMC Jeep, but is for similar vehicles of other manufacturers. I don't think AMC should be singled out," he said.

There are now 250,000 Jeep CJ5s on the road, and 21,000 of them were sold in 1979. American Motors has recently begun an aggressive sales campaign for the Jeep, and the CJ5 is the largest-selling four-wheel-drive utility vehicle.

The insurance institute said that the cause of the rollover for utility vehicles was high centers of gravity and comparatively narrow wheelbases. In addition, O'Neill said, the Jeep has a tendency to over-steer -- to respond too much to steering -- that makes it still more hazardous.

The institute added that the CJ5 has set a record in injury-frequency data. For insurance claims over $250, the CJ5 was 179 percent above the average in frequency of injury claims for all kinds of vehicles, and this figure was "the highest injury frequency result ever reported by the Highway Loss Date Institute" of the insurance industry.